GLP-1 and vitamins: what the TikTok hype gets wrong

What did @kweennx2fit actually say?

Not much, honestly. The creator said, "you have to make sure you're taking your supplements" while apparently showing a product to her 1.2 million viewers. That's the entire medical claim here. No specific supplements named, no dosages, no explanation of why. It's vague enough that it's hard to call wrong, but it's also vague enough to be potentially misleading depending on what she was holding up.

The GLP-1 community on TikTok has built a whole supplement culture around semaglutide and tirzepatide use. Some of it is grounded in real nutritional concerns. Some of it is people selling things. Without knowing what product she's showing, we're fact-checking the general claim that GLP-1 users need supplements, which is actually worth examining on its own.

Does the science back this up?

Yes, with significant caveats. GLP-1 receptor agonists reduce appetite substantially, which means people eat less. Eating less means taking in fewer micronutrients. That part is well-established and clinically relevant, not just influencer talk.

A 2023 review by Wilding et al. in Diabetes, Obesity and Metabolism noted that patients on semaglutide in the STEP trials lost significant lean muscle mass alongside fat, raising concerns about protein adequacy. Separately, research on post-bariatric patients, who experience similar dramatic caloric restriction, consistently shows deficiencies in vitamin B12, iron, vitamin D, and folate (Mechanick et al., 2020, Obesity). GLP-1 clinicians have started applying similar nutritional monitoring logic to their patients, though the evidence base specific to GLP-1 drugs is still catching up to clinical practice. The concern is legitimate. The prescription to just "take your supplements" is too blunt to be useful.

What did they get wrong (or right)?

She got the general direction right. GLP-1 users do face real nutritional risks that most people, and frankly many prescribers, underestimate. That's worth saying out loud.

What she got wrong, or at least incomplete, is the implication that supplements are a simple fix. The word "have to" implies a universal rule. It isn't one. Someone using a GLP-1 medication at a modest dose with a nutritionally dense diet and no underlying absorption issues may not need supplementation at all. Someone losing weight rapidly on tirzepatide while barely eating probably does. The difference matters.

There's also the muscle mass problem. Protein intake during GLP-1 therapy is arguably more important than any vitamin. A 2022 study by Biermann et al. in The Journal of Clinical Endocrinology and Metabolism found that adequate dietary protein helped preserve lean mass during weight loss interventions. Supplements like a multivitamin won't address that. Generic supplement advice without context about protein, caloric adequacy, and individual bloodwork is half a conversation.

What should you actually know?

If you're on a GLP-1 medication and eating significantly less than you used to, your micronutrient intake deserves attention. That's not alarmism, it's basic math. But the right answer isn't to grab whatever a TikTok creator is holding up to the camera.

The supplements most consistently flagged in clinical guidance for people on low-calorie regimens include:

• Vitamin B12, especially for those on metformin alongside GLP-1 drugs, since metformin independently depletes B12 (de Jager et al., 2010, BMJ)
• Vitamin D, which is commonly deficient in people with obesity independent of GLP-1 use
• Calcium, particularly if dairy intake drops
• Iron, especially in premenopausal women eating less red meat

None of this should come from a TikTok video. Get bloodwork. Talk to your prescriber or a registered dietitian who has actual experience with GLP-1 patients. The supplement industry does not need more customers buying random products because a viral video said "you have to."