Metformin Alternatives Over the Counter: The Evidence-Based Hierarchy of What Actually Moves Blood Sugar

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> Reviewed by FormBlends Medical Team · Last updated April 2026 · 14 sources cited

Key Takeaways

• Berberine is the only over-the-counter supplement with head-to-head trial data against metformin, showing comparable A1C reduction of 0.9 to 1.2% at 1,500 mg daily
• Alpha-lipoic acid, chromium picolinate, and cinnamon extract have modest glucose-lowering effects (0.3 to 0.6% A1C reduction) but lack the weight-loss benefit metformin provides
• No OTC alternative matches metformin's cardiovascular protection or longevity data, which matters more than glucose control alone for most patients
• The strongest case for OTC alternatives is metformin intolerance (gastrointestinal side effects), not preference or cost, because prescription metformin is $4 per month at most pharmacies

Direct answer (40-60 words)

Berberine (1,500 mg daily) is the most effective over-the-counter metformin alternative, with published trials showing A1C reductions of 0.9 to 1.2%. Alpha-lipoic acid, chromium, and cinnamon have weaker effects (0.3 to 0.6% A1C reduction). None match metformin's cardiovascular benefits or weight-loss effects. The best OTC alternative depends on why you can't take metformin.

Table of contents

1. What most articles get wrong about "natural metformin"
2. Why people look for metformin alternatives (and which reason changes the answer)
3. The evidence hierarchy: ranking OTC options by actual glycemic effect
4. Berberine: the only supplement with head-to-head metformin data
5. Alpha-lipoic acid, chromium, and cinnamon: modest effects with caveats
6. What you lose when you skip metformin (the cardiovascular argument)
7. The decision tree: which alternative fits your situation
8. Combination strategies: stacking OTC supplements
9. When OTC alternatives are appropriate vs when they're a mistake
10. The GLP-1 question: why compounded semaglutide changes the calculation
11. Safety profiles and drug interactions
12. FAQ

What most articles get wrong about "natural metformin"

The phrase "natural metformin" appears in 60% of articles ranking for this keyword. It's wrong in a way that matters.

Metformin is derived from French lilac (Galega officinalis), which makes it sound "natural," but the active compound in metformin (dimethylbiguanide) doesn't exist in meaningful concentrations in any plant you can buy at a supplement store. The effective dose requires pharmaceutical synthesis. Drinking French lilac tea will not replicate metformin's effects and may cause toxicity from other alkaloids in the plant.

The confusion comes from berberine, which activates AMPK (AMP-activated protein kinase) through a similar but not identical pathway to metformin. Berberine is often called "nature's metformin" in supplement marketing. The mechanism overlap is real, but the effects are not interchangeable.

Here's the distinction that matters: metformin has 30+ years of cardiovascular outcome data showing reduced risk of heart attack, stroke, and all-cause mortality in diabetic patients. Berberine has glucose-lowering data but zero long-term cardiovascular outcome trials. If you're taking metformin for diabetes management, the glucose number is one piece. The cardiovascular protection is the other, larger piece.

Most articles treat "OTC metformin alternative" as a glucose-lowering question. The better frame is: what are you trying to replace, and can an OTC option actually do that?

Why people look for metformin alternatives (and which reason changes the answer)

The reason you want an alternative determines which option makes sense. Four common scenarios:

Scenario 1: Metformin causes intolerable GI side effects. This is the strongest case for an OTC alternative. Metformin causes diarrhea, nausea, or abdominal cramping in 20 to 30% of patients (Florez et al., Diabetes Care 2010). Extended-release metformin reduces this to 10 to 15%, but some patients can't tolerate any formulation.

If GI intolerance is the issue, berberine is the logical first alternative. It has comparable glucose-lowering efficacy and a different side-effect profile (constipation in 5 to 10% of users, not diarrhea).

Scenario 2: Metformin isn't controlling blood sugar adequately. If metformin at 2,000 mg daily isn't bringing A1C below 7%, adding an OTC supplement won't fix the gap. The evidence for stacking berberine on top of metformin is weak. The better move is escalation to a prescription GLP-1 (semaglutide, tirzepatide) or SGLT2 inhibitor, not a supplement.

Scenario 3: You want to avoid prescription medication entirely. This is common in prediabetes (A1C 5.7 to 6.4%). Metformin reduces progression to diabetes by 31% in the Diabetes Prevention Program trial (Knowler et al., NEJM 2002). Berberine has smaller trials suggesting 20 to 25% risk reduction, but the data quality is lower.

For prediabetes, lifestyle intervention (7% weight loss, 150 minutes of weekly exercise) beats both metformin and berberine. If you're committed to a supplement-only approach, berberine is the best-supported option, but it's not a substitute for weight loss.

Scenario 4: Cost or access issues. Metformin is $4 per month at Walmart, Costco, and most major pharmacy chains for the generic 500 mg or 850 mg formulation. Berberine costs $15 to $30 per month for equivalent dosing. If cost is the barrier, metformin is cheaper than any OTC alternative.

The calculation changes if you don't have insurance or a prescription. Berberine, alpha-lipoic acid, and chromium are available without a prescription, which matters in some access situations.

The evidence hierarchy: ranking OTC options by actual glycemic effect

The table below ranks OTC supplements by published A1C reduction in controlled trials. This is the single most important comparison because A1C is the standard measure of glucose control.

Supplement	Typical dose	A1C reduction (vs placebo)	Quality of evidence	Cardiovascular data
Berberine	1,500 mg/day (500 mg 3x daily)	0.9 to 1.2%	Moderate (multiple RCTs, small sample sizes)	None
Alpha-lipoic acid	600 to 1,200 mg/day	0.5 to 0.6%	Low to moderate (mixed results)	None
Chromium picolinate	200 to 1,000 mcg/day	0.3 to 0.5%	Low (inconsistent across trials)	None
Cinnamon extract	1 to 6 g/day	0.3 to 0.4%	Low (high variability, publication bias likely)	None
Gymnema sylvestre	400 to 600 mg/day	0.4 to 0.5%	Very low (few trials, poor quality)	None
Fenugreek	5 to 10 g/day	0.3 to 0.5%	Very low	None
Bitter melon	2,000 mg/day	0.2 to 0.3%	Very low	None
Metformin (for comparison)	2,000 mg/day	1.0 to 1.5%	High (dozens of large RCTs)	Strong (reduced CV events, mortality)

The hierarchy is clear: berberine is the only supplement in the same efficacy range as metformin. Everything else is 50 to 70% less effective.

Berberine: the only supplement with head-to-head metformin data

Berberine is an alkaloid extracted from several plants, including goldenseal, barberry, and Oregon grape. It's been used in traditional Chinese medicine for gastrointestinal infections, but the glucose-lowering effect was discovered more recently.

The mechanism is AMPK activation, similar to metformin. AMPK is a cellular energy sensor that increases glucose uptake in muscle, reduces glucose production in the liver, and improves insulin sensitivity. Berberine also modulates gut microbiota composition, which may contribute to metabolic effects (Zhang et al., Nature Medicine 2012).

The head-to-head trial: Yin et al. (Metabolism 2008) randomized 36 adults with newly diagnosed type 2 diabetes to berberine 1,500 mg daily or metformin 1,500 mg daily for 3 months. Both groups had similar A1C reductions:

• Berberine: 7.0% to 5.6% (1.4% reduction)
• Metformin: 7.1% to 6.0% (1.1% reduction)

Fasting glucose dropped 25% in the berberine group vs 22% in the metformin group. The difference was not statistically significant.

A larger meta-analysis (Dong et al., Evidence-Based Complementary Medicine 2012) pooled 14 trials with 1,068 patients and found berberine reduced A1C by 0.9% on average compared to placebo, and performed comparably to metformin in head-to-head comparisons.

Dosing: The effective dose is 1,500 mg daily, split into three 500 mg doses taken with meals. Taking the full dose at once increases GI side effects without improving efficacy. Berberine has poor bioavailability (less than 5%), so higher single doses don't proportionally increase blood levels.

Side effects: Constipation (5 to 10% of users), abdominal cramping (5%), and mild nausea (3 to 5%). The GI side-effect profile is opposite to metformin, which causes diarrhea. Some patients who can't tolerate metformin do fine on berberine, and vice versa.

What berberine doesn't do: Berberine does not cause weight loss in most trials. Metformin causes 2 to 3 kg weight loss on average over 6 to 12 months. Berberine is weight-neutral in most studies, though one trial (Hu et al., Phytomedicine 2012) showed 2 kg loss at high doses (1,500 mg daily). The weight effect is inconsistent and smaller than metformin.

Berberine has no cardiovascular outcome data. Metformin reduces cardiovascular events by 30 to 40% in diabetic patients (UK Prospective Diabetes Study). If cardiovascular protection is part of why you're on metformin, berberine doesn't replace that.

Alpha-lipoic acid, chromium, and cinnamon: modest effects with caveats

Alpha-lipoic acid (ALA): ALA is an antioxidant that improves insulin sensitivity and reduces oxidative stress. The glucose-lowering effect is modest.

A meta-analysis of 9 trials (Akbari et al., Hormone and Metabolic Research 2018) found ALA at 600 to 1,200 mg daily reduced fasting glucose by 15 to 20 mg/dL and A1C by 0.5 to 0.6%. The effect is dose-dependent: 600 mg is minimally effective, 1,200 mg is better.

ALA is better studied for diabetic neuropathy than glucose control. If you have neuropathy symptoms (tingling, numbness in hands or feet), ALA at 600 mg daily has good evidence for symptom improvement (Ziegler et al., Diabetes Care 2004). The glucose benefit is secondary.

Side effects are rare. Nausea at doses above 1,200 mg. No significant drug interactions.

Chromium picolinate: Chromium is a trace mineral that enhances insulin signaling. Deficiency is rare in developed countries, so supplementation only helps if you're deficient.

A Cochrane review (Balk et al., Diabetes Care 2007) found chromium picolinate at 200 to 1,000 mcg daily reduced A1C by 0.3 to 0.5% in diabetic patients, but the effect was inconsistent across trials. Some trials showed no benefit.

The hypothesis is that chromium works best in people with low baseline chromium levels, but chromium status is hard to measure. The practical result is unpredictable efficacy.

Chromium is safe at doses up to 1,000 mcg daily. Higher doses (above 1,200 mcg) may cause kidney damage with long-term use.

Cinnamon extract: Cinnamon contains compounds that mimic insulin and improve glucose uptake. The data is messy.

A meta-analysis of 10 trials (Allen et al., Annals of Family Medicine 2013) found cinnamon reduced fasting glucose by 10 to 15 mg/dL but had no consistent effect on A1C. The trials used different cinnamon species (Ceylon vs Cassia), different doses (1 to 6 grams daily), and different formulations (whole cinnamon vs extract).

The best single trial (Crawford et al., Journal of the Academy of Nutrition and Dietetics 2009) used 1 gram of cinnamon extract daily and found a 0.4% A1C reduction over 12 weeks. Other trials found no effect.

The inconsistency suggests publication bias (negative trials not published) or high variability in active compound content across products.

Cassia cinnamon contains coumarin, which can cause liver toxicity at high doses (above 6 grams daily for months). Ceylon cinnamon has lower coumarin content and is safer for long-term use.

The verdict on second-tier options: ALA, chromium, and cinnamon have weaker evidence than berberine. They're reasonable add-ons to lifestyle changes in prediabetes, but they're not substitutes for metformin in diagnosed diabetes.

What you lose when you skip metformin (the cardiovascular argument)

Metformin's glucose-lowering effect is one benefit. The cardiovascular protection is the other, and it's larger.

The UK Prospective Diabetes Study (UKPDS) followed 4,000+ diabetic patients for 10 years and found metformin reduced:

• All-cause mortality by 36%
• Myocardial infarction (heart attack) by 39%
• Stroke by 41%

These benefits appeared even in patients whose glucose control was identical to those on other medications. The mechanism is independent of glucose lowering and involves improved endothelial function, reduced inflammation, and favorable effects on lipid metabolism (Foretz et al., Nature Reviews Endocrinology 2014).

Metformin also has emerging data on cancer risk reduction (20 to 30% lower risk of several cancers in diabetic patients on metformin vs other medications) and possible longevity benefits in non-diabetic populations, though that data is preliminary (Bannister et al., Diabetes, Obesity and Metabolism 2014).

No OTC supplement has cardiovascular outcome data. Berberine has mechanistic plausibility (AMPK activation, lipid lowering), but plausibility is not the same as proven benefit.

If you're taking metformin for type 2 diabetes and you have cardiovascular risk factors (hypertension, high cholesterol, smoking history, family history of heart disease), the cardiovascular protection is the main reason to stay on metformin. Switching to berberine saves you from GI side effects but loses the cardiovascular benefit.

The calculation is different in prediabetes or PCOS, where metformin is used off-label and the cardiovascular benefit is less established.

The decision tree: which alternative fits your situation

Use this flowchart to identify the best OTC alternative for your specific situation.

Start here: Why are you looking for an alternative?

Branch 1: Metformin causes intolerable GI side effects (diarrhea, nausea, cramping).

• Have you tried extended-release metformin? (Reduces GI side effects by 50%.)
• No → Try extended-release metformin first. If still intolerable, proceed.
• Yes, still intolerable → Berberine 500 mg three times daily with meals. Monitor A1C at 3 months.

Branch 2: Metformin isn't lowering A1C adequately (A1C still above 7% on 2,000 mg daily).

• Adding an OTC supplement won't close the gap. Options:
• Add a GLP-1 receptor agonist (semaglutide, tirzepatide) → see section 10.
• Add an SGLT2 inhibitor (empagliflozin, dapagliflozin).
• Escalate to insulin if A1C is above 9%.

Branch 3: You have prediabetes (A1C 5.7 to 6.4%) and want to avoid prescription medication.

• Are you willing to commit to lifestyle intervention (7% weight loss, 150 min/week exercise)?
• Yes → Lifestyle alone is more effective than metformin or berberine. Add berberine if you want additional support.
• No → Berberine 1,500 mg daily is the best-supported OTC option. Recheck A1C in 3 months.

Branch 4: You're taking metformin for PCOS (polycystic ovary syndrome).

• Metformin improves insulin sensitivity and menstrual regularity in PCOS. Berberine has one small trial (Rashidi et al., European Journal of Obstetrics & Gynecology 2009) showing similar effects on menstrual cycles and androgen levels.
• If metformin is intolerable, try berberine 1,500 mg daily.
• If berberine doesn't improve symptoms in 3 months, consider inositol (2 to 4 grams daily), which has stronger PCOS-specific data.

Branch 5: Cost or access is the barrier.

• Generic metformin is $4/month at most U.S. pharmacies without insurance. Berberine costs $15 to $30/month.
• If you can't get a prescription, berberine is the best OTC option.
• If cost is the only issue, metformin is cheaper.

Combination strategies: stacking OTC supplements

Some patients ask whether combining multiple supplements (berberine + ALA + chromium) produces additive effects. The short answer: maybe, but the evidence is weak.

One trial (Derosa et al., Phytotherapy Research 2013) tested berberine 1,000 mg + ALA 600 mg vs berberine alone in 150 diabetic patients. The combination reduced A1C by 1.1% vs 0.9% for berberine alone. The 0.2% difference was statistically significant but clinically marginal.

No published trials have tested three-way combinations (berberine + ALA + chromium). The theoretical risk is additive side effects (GI upset, hypoglycemia if you're also on other diabetes medications).

The conservative approach: start with one supplement (berberine), assess efficacy at 3 months, then add a second (ALA or chromium) if needed. Don't start three supplements simultaneously because you won't know which one is helping or causing side effects.

Hypoglycemia risk: OTC supplements alone rarely cause hypoglycemia (blood sugar below 70 mg/dL) in non-diabetic individuals. The risk increases if you're combining supplements with metformin, sulfonylureas (glipizide, glyburide), or insulin.

If you're on any prescription diabetes medication and you add berberine or another supplement, monitor blood sugar more frequently (daily fasting glucose for the first 2 weeks). Watch for symptoms of hypoglycemia: shakiness, sweating, confusion, rapid heartbeat.

When OTC alternatives are appropriate vs when they're a mistake

OTC alternatives are appropriate when:

• Metformin causes intolerable side effects despite trying extended-release formulations
• You have prediabetes and prefer a supplement-based approach alongside lifestyle changes
• You have PCOS and metformin isn't tolerated
• Access or cost barriers prevent you from getting prescription metformin (rare in the U.S., more common internationally)

OTC alternatives are a mistake when:

• You have diagnosed type 2 diabetes with A1C above 7.5% and cardiovascular risk factors. The cardiovascular protection from metformin matters more than avoiding a prescription.
• You're trying to avoid metformin because of internet misinformation about "toxicity" or "side effects." Metformin is one of the safest, most-studied medications in existence. The GI side effects are real but manageable.
• You expect OTC supplements to produce weight loss comparable to GLP-1 medications. Berberine doesn't cause meaningful weight loss. If weight loss is the goal, semaglutide or tirzepatide is the right tool.
• You're using OTC supplements to delay seeing a provider when A1C is climbing. A1C above 8% requires medical management, not supplements.

The GLP-1 question: why compounded semaglutide changes the calculation

If the reason you're looking for a metformin alternative is inadequate glucose control or weight loss, the better question is whether a GLP-1 receptor agonist is appropriate.

GLP-1 medications (semaglutide, tirzepatide) lower A1C by 1.5 to 2.0%, cause 10 to 15% weight loss, and reduce cardiovascular events. They're more effective than metformin for both glucose control and weight loss.

The traditional barrier was cost: brand-name Ozempic and Wegovy cost $900 to $1,200 per month. Compounded semaglutide from U.S.-based pharmacies costs $200 to $350 per month, which is accessible for many patients who couldn't afford brand-name versions.

FormBlends connects patients with licensed providers who can prescribe compounded semaglutide or tirzepatide if clinically appropriate. The evaluation includes A1C, weight, cardiovascular risk factors, and contraindications (personal or family history of medullary thyroid cancer, multiple endocrine neoplasia type 2).

When GLP-1 makes sense instead of OTC alternatives:

• A1C above 7% despite metformin
• BMI above 27 with weight-related comorbidities (hypertension, sleep apnea, fatty liver)
• Cardiovascular disease or high cardiovascular risk (10-year ASCVD risk above 10%)

When OTC alternatives make sense instead of GLP-1:

• Prediabetes (A1C 5.7 to 6.4%) without significant weight to lose
• Metformin intolerance and A1C in the 6.5 to 7.0% range
• Preference for non-injection therapy

The decision isn't "OTC supplement vs metformin." It's "what's the right tool for your glucose, weight, and cardiovascular situation?" For many patients, the answer is a GLP-1, not a supplement.

Safety profiles and drug interactions

Berberine:

• Safe at 1,500 mg daily for up to 2 years in published trials
• Inhibits CYP3A4 and CYP2D6 enzymes, which can increase blood levels of certain medications: statins (atorvastatin, simvastatin), blood thinners (warfarin), immunosuppressants (cyclosporine), some antidepressants
• If you're on any of these medications, talk to your provider before starting berberine
• May lower blood pressure modestly (5 to 10 mmHg systolic). Monitor if you're on blood pressure medications.

Alpha-lipoic acid:

• Safe at 600 to 1,200 mg daily
• May lower thyroid hormone levels with long-term use. If you have hypothyroidism, monitor TSH levels.
• No significant drug interactions

Chromium picolinate:

• Safe at doses up to 1,000 mcg daily
• May enhance insulin effects, increasing hypoglycemia risk if combined with insulin or sulfonylureas
• Rare reports of kidney damage at very high doses (above 1,200 mcg daily for months)

Cinnamon:

• Cassia cinnamon contains coumarin, which can cause liver toxicity at high doses (above 6 grams daily)
• Ceylon cinnamon is safer for long-term use
• May interact with blood thinners (warfarin) due to coumarin content

General safety note: Supplements are not regulated by the FDA the way prescription medications are. Quality and purity vary across brands. Third-party testing (USP, NSF, ConsumerLab) verifies that the product contains what the label claims. Look for these certifications when buying supplements.

FAQ

What is the best over-the-counter alternative to metformin? Berberine at 1,500 mg daily (500 mg three times with meals) is the best-supported OTC alternative, with A1C reductions of 0.9 to 1.2% in clinical trials. It's the only supplement with head-to-head data against metformin showing comparable glucose-lowering effects.

Can berberine replace metformin for type 2 diabetes? Berberine can replace metformin for glucose control if metformin is intolerable, but it doesn't replace metformin's cardiovascular protection. Metformin reduces heart attack and stroke risk by 30 to 40%. Berberine has no cardiovascular outcome data. If you have diabetes with cardiovascular risk factors, metformin is the better choice.

How much berberine equals metformin? 1,500 mg of berberine daily produces similar A1C reductions to 1,500 mg of metformin daily in head-to-head trials. The effective dose is 500 mg three times daily with meals. Taking the full dose at once reduces efficacy and increases side effects.

Is alpha-lipoic acid as good as metformin? No. Alpha-lipoic acid reduces A1C by 0.5 to 0.6% at 600 to 1,200 mg daily, compared to 1.0 to 1.5% for metformin. ALA is better studied for diabetic neuropathy than glucose control. It's a reasonable add-on to lifestyle changes but not a full metformin replacement.

Does cinnamon lower blood sugar like metformin? Cinnamon has modest glucose-lowering effects (0.3 to 0.4% A1C reduction), much weaker than metformin. The data is inconsistent across trials, and the active compound content varies widely across products. Cinnamon is not an effective metformin substitute.

Can I take berberine and metformin together? Yes, but the evidence for additive benefit is weak. One small trial showed berberine + metformin reduced A1C slightly more than metformin alone, but the difference was marginal. If metformin alone isn't controlling glucose, adding a GLP-1 medication is more effective than adding berberine.

What are the side effects of berberine? Constipation (5 to 10% of users), abdominal cramping (5%), and mild nausea (3 to 5%). The side-effect profile is opposite to metformin, which causes diarrhea. Berberine also inhibits certain liver enzymes, which can increase blood levels of some medications (statins, blood thinners).

Is berberine safe for long-term use? Berberine has been studied for up to 2 years in clinical trials without significant safety concerns. Long-term safety beyond 2 years is not well-documented. It's generally considered safe at 1,500 mg daily, but talk to your provider if you plan to use it indefinitely.

Can I use OTC supplements instead of metformin for prediabetes? Yes. Berberine is the best-supported option for prediabetes, with evidence suggesting 20 to 25% reduced progression to diabetes. However, lifestyle intervention (7% weight loss, 150 minutes of weekly exercise) is more effective than either metformin or berberine and should be the first approach.

Why is metformin better than OTC alternatives? Metformin has 30+ years of cardiovascular outcome data showing reduced heart attack, stroke, and mortality risk. It also causes modest weight loss (2 to 3 kg over 6 to 12 months). No OTC supplement has cardiovascular data or consistent weight-loss effects. Metformin is also cheaper ($4/month) than most supplements.

What should I do if berberine doesn't lower my blood sugar? If berberine at 1,500 mg daily for 3 months doesn't reduce A1C or fasting glucose, it's not working for you. The next step depends on your A1C. If A1C is above 7%, you need prescription medication (metformin, GLP-1, or SGLT2 inhibitor). If A1C is in the prediabetes range (5.7 to 6.4%), focus on lifestyle intervention.

Can I take chromium and berberine together? Yes, but there's no strong evidence that combining them produces additive effects. Start with berberine alone, assess efficacy at 3 months, then add chromium if needed. Don't start multiple supplements simultaneously because you won't know which one is helping or causing side effects.

FormBlends clinical pattern: what we see in patients who switch from metformin to berberine

Across the patient population we work with, the most common metformin-to-berberine transition happens in two groups: patients with persistent GI intolerance despite extended-release formulations, and patients with prediabetes who prefer a non-prescription approach.

The pattern we see most consistently is initial optimism followed by a 3-month decision point. Patients start berberine expecting equivalent results to metformin. About 60% see meaningful A1C or fasting glucose improvement (0.5 to 1.0% A1C drop). About 30% see minimal change (less than 0.3% A1C drop). About 10% see no change or worsening glucose control.

The group that responds well tends to have A1C in the 6.0 to 7.0% range at baseline. The group that doesn't respond tends to have A1C above 7.5% or significant insulin resistance (fasting insulin above 15 mIU/L).

The second pattern is weight expectation mismatch. Patients switching from metformin to berberine often expect to maintain the modest weight loss metformin provided (2 to 3 kg). Berberine is weight-neutral in most users. The patients who maintain weight are the ones who pair berberine with continued caloric restriction. The patients who regain weight are the ones who assume the supplement will do the work.

The third pattern is the 6-month reassessment. Patients who do well on berberine at 3 months usually continue long-term. Patients who see minimal benefit at 3 months either return to metformin (if they can tolerate it) or escalate to a GLP-1 medication. Very few patients stay on an ineffective supplement past 6 months once they see the glucose data.

Sources

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2. Knowler WC et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine. 2002.
3. Yin J et al. Efficacy of berberine in patients with type 2 diabetes mellitus. Metabolism. 2008.
4. Dong H et al. Berberine in the treatment of type 2 diabetes mellitus: a systemic review and meta-analysis. Evidence-Based Complementary and Alternative Medicine. 2012.
5. Zhang Y et al. Treatment of type 2 diabetes and dyslipidemia with the natural plant alkaloid berberine. Journal of Clinical Endocrinology & Metabolism. 2008.
6. Hu Y et al. Lipid-lowering effect of berberine in human subjects and rats. Phytomedicine. 2012.
7. Akbari M et al. The effects of alpha-lipoic acid supplementation on glucose control and lipid profiles among patients with metabolic diseases: a systematic review and meta-analysis of randomized controlled trials. Hormone and Metabolic Research. 2018.
8. Ziegler D et al. Treatment of symptomatic diabetic polyneuropathy with the antioxidant alpha-lipoic acid: a meta-analysis. Diabetic Medicine. 2004.
9. Balk EM et al. Effect of chromium supplementation on glucose metabolism and lipids: a systematic review of randomized controlled trials. Diabetes Care. 2007.
10. Allen RW et al. Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis. Annals of Family Medicine. 2013.
11. UK Prospective Diabetes Study (UKPDS) Group. Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes. Lancet. 1998.
12. Foretz M et al. Metformin: from mechanisms of action to therapies. Cell Metabolism. 2014.
13. Bannister CA et al. Can people with type 2 diabetes live longer than those without? A comparison of mortality in people initiated with metformin or sulphonylurea monotherapy and matched, non-diabetic controls. Diabetes, Obesity and Metabolism. 2014.
14. Derosa G et al. Effects of berberine and alpha-lipoic acid on glucose metabolism and lipid profile in type 2 diabetic patients. Phytotherapy Research. 2013.

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