Tirzepatide dosing on TikTok: what the clinical data says

What did @keepingwithkirsty actually say?

The creator's core claim is straightforward: in Australia, tirzepatide prescriptions are written in milligrams, but what you actually inject is measured in milliliters. She states the starting dose is "2.5 milligrams" which "equates to 0.25 milliliters," and warns viewers not to inject "2.5 mils of product" because that would be a dangerous overdose.

She's responding to apparent viewer confusion about why she discusses her dose in milligrams while the physical act of injection involves a milliliter measurement. The video references a peptide vial that displays both units, and she uses this to explain the conversion. Her warning is blunt: injecting 2.5 milliliters instead of 0.25 milliliters would be "an astronomical amount of product" that could cause serious harm.

This is a patient-to-patient explainer, not a clinical consultation. That framing matters when evaluating what she got right and where the gaps are.

Does the science back this up?

The unit conversion logic she describes is broadly correct, but the specific numbers she gives depend entirely on the concentration of the preparation being used, which she never states. That omission is the single biggest problem here.

Tirzepatide as sold under the brand name Mounjaro in Australia comes in prefilled autoinjectors at fixed doses: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. These pens deliver a fixed volume, and users don't calculate milliliters at all. The mg-to-mL math she describes, where 2.5 mg equals 0.25 mL, only holds if the solution is at a concentration of 10 mg/mL. Compounded tirzepatide preparations can and do vary in concentration. If a compounded vial is at 5 mg/mL, 2.5 mg would be 0.5 mL. If it's at 20 mg/mL, 2.5 mg is 0.125 mL. Without knowing the concentration, the conversion is not something viewers should apply to their own vials. Research on medication errors in self-administered injectables consistently identifies unit confusion and concentration misreading as leading causes of dosing mistakes (Keers et al., 2014, Drug Safety).

What did they get wrong (or right)?

She got the conceptual framework right. Prescribed doses in mass units and injected volumes in liquid units are genuinely different things, and that distinction does confuse people. Her warning against injecting 2.5 milliliters is also correct in spirit: that volume would represent a massive overdose under almost any realistic tirzepatide concentration.

What she got wrong, or at least dangerously incomplete, is implying that her specific conversion applies universally. The statement that 2.5 mg "equates to 0.25 milliliters" is only true at a specific concentration, and she never states what that concentration is. A viewer watching this video with a differently concentrated vial could use her numbers and inject the wrong dose entirely.

She also uses the phrase "peptide vial" without clarifying whether she is using a compounded product or a licensed medicine. This matters because compounded tirzepatide preparations are not equivalent to branded Mounjaro, and the concentration varies by compounding pharmacy. That distinction should be made explicit, not assumed.

What should you actually know?

If you are using a vial-and-syringe tirzepatide preparation, the only conversion that matters is the one printed on your specific vial or provided by your prescribing doctor or pharmacist. The formula is simple: volume (mL) equals dose (mg) divided by concentration (mg/mL). You cannot skip the concentration step.

For context, the SURMOUNT-1 trial (Jastreboff et al., 2022, New England Journal of Medicine) established the tirzepatide dosing schedule used in clinical practice: starting at 2.5 mg weekly and titrating in 2.5 mg increments every four weeks. That trial used the brand-name formulation at defined concentrations. Compounded versions are not studied in the same trials and may differ in bioavailability, excipients, and concentration.

• Always confirm the concentration (mg/mL) on your vial before calculating a volume to inject.
• Mounjaro autoinjectors in Australia do not require milliliter calculations. If you are doing the math yourself, you are likely using a compounded product.
• Your prescribing doctor or dispensing pharmacist should provide explicit volume instructions for your specific preparation.
• A 10-fold dosing error (injecting mL as if it were mg) is a real and documented risk in injectable medications.

The bottom line

This video is well-intentioned and the core message, that mg and mL are different units and confusing them is dangerous, is correct. But the specific conversion numbers she gives are only valid for one particular concentration, and she never tells viewers what that concentration is. For a platform like TikTok where viewers may be using preparations with different concentrations, presenting a single mg-to-mL conversion as universal is the kind of partial truth that causes dosing errors. Credit where it's due: the overdose warning is the right call. But dosage instructions need the concentration context to be safe, full stop.