GLP-1 Dosage Calculator

It converts a target weekly GLP-1 dose (in mg/week) and a vial concentration (in mg/mL) into the milligrams and millilitres you would draw per injection across common dosing intervals - daily, every other day, twice weekly, weekly, or a custom schedule. It also estimates the marking on a U-100 insulin syringe, full doses per vial, and days of supply.

U-100 insulin syringes are marked in units where 100 units equal 1 mL (so 1 unit equals 0.01 mL). The calculator multiplies your draw volume in mL by 100 to give you the unit marking - for example, a 0.07 mL draw is 7 units. Always confirm against the markings on your specific syringe before drawing.

Compounded GLP-1 vials typically ship at 5 mg/mL or 10 mg/mL for semaglutide, and 5 mg/mL or 10 mg/mL for tirzepatide. Branded products ship in pre-filled pens with fixed per-click dosing and are not the use case for this tool. Always confirm the concentration printed on the vial label before calculating.

Pick a frequency in the calculator (e.g. twice weekly or every other day) and the math will divide your weekly target across the resulting doses. Splitting evenly across the week can smooth side effects for some people, but the steady-state weekly exposure is the same as a single injection. Always check with your prescriber before changing your interval.

A partial last dose is not a useful planning unit for most users, so the calculator floors the result and reports the leftover volume as a remainder. "Days of supply" only counts whole doses, so it will never overstate how long a vial lasts.

Partially. The dose-conversion math (mg per injection, mL per draw, vial usage) is purely arithmetic and identical across drugs. The 'Estimated drug levels' chart, however, uses each drug's terminal half-life (semaglutide ~7 days, tirzepatide ~5 days, retatrutide ~6 days, dulaglutide ~5 days, liraglutide ~13 hours) so the relative curve and time-to-steady-state estimates differ per drug. The chart does not model receptor binding, potency, or absolute plasma concentration. Use it for sequence and timing intuition, not protocol selection - see the disclaimer.

Roughly 4.32 times the drug's terminal half-life. For semaglutide (t1/2 ~7 days) that's about 4-5 weeks. For tirzepatide and dulaglutide (t1/2 ~5 days) it's about 3 weeks. Liraglutide reaches steady state in 2-3 days because of its 13-hour half-life. The 'Estimated drug levels' chart marks the ~95% steady-state crossover with a vertical dashed line so you can read the date directly. Note that *time* to steady state is independent of dosing interval - the dosing interval only changes the *number* of doses required to get there.

It's the steady-state peak divided by the trough at the chosen dosing interval, calculated as 1 / (1 - e^(-k × tau)) where k is ln(2) divided by the terminal half-life and tau is your interval in hours. Semaglutide weekly accumulates ~2x; tirzepatide weekly accumulates ~1.6x; liraglutide daily accumulates ~1.04x (essentially no accumulation). A higher ratio means you'll have more drug on board at peak vs. trough between injections.

It depends on the drug and how late you are. The calculator's 'Did you miss a dose?' panel restates each brand's labelled rule and computes a take-now / skip recommendation from the date you pick. Quick reference: semaglutide (Ozempic / Wegovy) - take if at least 2 days remain until the next dose, otherwise skip. Tirzepatide (Mounjaro / Zepbound) - take if remembered within 4 days of the missed schedule, otherwise skip. Dulaglutide (Trulicity) - take if at least 3 days remain until the next dose. Liraglutide (Victoza / Saxenda) - take if remembered within ~12 hours, otherwise skip. Never double up to make up for a missed dose. Confirm with your prescriber.

Enter what you pay per vial in the 'Refill cost' card and the calculator divides into $/mg, $/week, $/month, and $/year at your current weekly dose. The $/mg number is especially useful for cross-vial comparison: if compounder A sells a 5 mg semaglutide vial for $200 and compounder B sells a 10 mg vial for $300, A is $40/mg and B is $30/mg - B is cheaper per mg even though the sticker price is higher. The math assumes the same vial price across all your refills and doesn't model insurance reimbursement, manufacturer coupons, or bulk-order discounts. For brand-name reference points: Wegovy and Zepbound retail near $1,300-$1,400 per pen at full price; compounded semaglutide and tirzepatide typically run $200-$500 per multi-dose vial.

Hard to predict for any individual, but the population pattern is consistent: GLP-1 GI side effects (nausea, fatigue, constipation, occasionally vomiting) typically spike 3-7 days after a dose increase and resolve over the following 1-2 weeks. The 'GI tolerance forecast' line above the schedule projects each dose-up in your titration plan as a rough patch with a 'mild' / 'moderate' / 'rough' intensity bucket based on the relative size of the bump (a +25% increase is mild; a +50% is moderate; doubling is rough). This is a *population pattern*, not a personal prediction — interquartile range often spans 'barely noticed' to 'had to pause titration'. If a forecast bump lands during a high-stakes week (work travel, big event), consider asking your prescriber about delaying the step-up.

The 'Refill timeline' line inside the Vial usage card resolves your inventory into per-vial coverage dates and surfaces an 'Order next vial by [date]' recommendation. The default lead time is 7 days (typical compounded GLP-1 shipping window). For a 2 mL semaglutide vial at 10 mg/mL dosed 2.4 mg/wk, the math is: 8 doses × 7 days = 56 days of supply; if your first dose lands on May 7 the inventory depletes Jul 2, so order by Jun 25. Multi-vial inventories show coverage handoff dates between vials. The recommendation is purely arithmetic and does not account for shipping delays, prescription approvals, or refrigeration constraints.

There is no FDA-approved equipotency table between GLP-1 receptor agonists. The 'Considering a switch?' card on this calculator maps your current drug + dose to a *weight-loss-effect equivalent* on a target drug, using trial-mean weight-loss percentages from STEP (semaglutide), SURMOUNT (tirzepatide), AWARD (dulaglutide), SCALE (liraglutide), and TRIUMPH-1 (retatrutide). Rough reference points: semaglutide 1 mg/wk ≈ tirzepatide 5 mg/wk (~7-8% weight loss); semaglutide 2.4 mg/wk ≈ tirzepatide 10 mg/wk (~15%). When switching, always (1) stop the current drug, (2) wait one full dosing interval (~7 days for weekly drugs, 1 day for daily liraglutide), and (3) start the new drug at its labelled starter dose - NOT the equivalent maintenance dose - and titrate up over weeks. Jumping straight to the equivalent dose causes severe GI side effects. Confirm any switch with your prescriber.

It's the total millilitres you would draw over a full week at steady state, calculated as weekly_mg divided by concentration_mg_per_mL. It's useful for forecasting how many vials you need across a multi-month plan and for sanity-checking your per-injection volume against your weekly target.

No. The site is for educational dose conversion and PK intuition only. Every formula is grounded in a citable source (FDA prescribing information, USP/ISO standards, or peer-reviewed pharmacokinetics references), but a cited formula speaks only to the mathematical claim - not to whether the calculator output is appropriate for any specific person. Always confirm any number with a licensed clinician and the actual product labelling for your medication. See the disclaimer for the full statement.