Dosia Medication-level estimates

GLP-1 medication-level estimates: what they are, and why they are not blood levels

A GLP-1 medication-level estimate is a modeled curve showing how the amount of a medication in the body might rise and fall over time. It is calculated from the doses you log and the medication's published pharmacokinetic data, such as half-life. In Dosia, the curve shows an estimated amount remaining in the body (in mg). It is not a measured blood concentration and must not be used to make dosing or treatment decisions.

The short version

  • An estimate comes from a model, not from a blood sample.
  • It is based on your logged doses and timing and on published pharmacokinetic data, such as half-life.
  • FDA labels give an elimination half-life of about 1 week for semaglutide (Ozempic®, Wegovy®, Rybelsus®) and about 5 days for tirzepatide (Mounjaro®; Zepbound® lists about 5–6 days in patients with overweight or obesity).
  • Real levels vary from person to person. An estimate cannot show your individual level.
  • Use estimates to understand your timeline and to talk with your clinician. Never use them to change a dose.

Half-life in plain language

A drug's elimination half-life is the time it takes for the amount of the drug in the body to fall by half. The NIH's StatPearls reference describes it as "the time required for the concentration of a specific substance, typically a drug, to decrease to half of its initial amount in the body." [1]

Two general ideas follow from half-life [1][2]:

  • Gradual decline. After one half-life, about half remains; after another, about a quarter; and so on.
  • Build-up to a steady state. When a medicine is taken on a regular schedule, levels build up over several half-lives until intake and elimination balance out. StatPearls notes this typically takes about 4 to 5 half-lives. [1]

This is why long-acting GLP-1 medicines with half-lives of several days are taken once weekly, and why their labels describe steady state being reached after several weeks.

Published half-lives of common GLP-1 medications

Figures are quoted from each medication's FDA prescribing information (section 12.3, Pharmacokinetics) as published on DailyMed. They describe study populations, not any individual.

Medication (active ingredient) Elimination half-life, per FDA label Other label PK notes Source
Ozempic® (semaglutide injection) "an elimination half-life of approximately 1 week" "Maximum concentration of semaglutide is reached 1 to 3 days post dose." "Steady-state exposure is achieved following 4 to 5 weeks of once-weekly administration." [3]
Wegovy® (semaglutide) "an elimination half-life of approximately 1 week" Injection: "Maximum concentration of semaglutide is reached 1 to 3 days post dose." [4]
Rybelsus® (oral semaglutide) "Semaglutide elimination half-life is approximately one week" — [5]
Mounjaro® (tirzepatide) "an elimination half-life of approximately 5 days, enabling once-weekly dosing" "the time to maximum plasma concentration of tirzepatide ranges from 8 to 72 hours." "Steady-state plasma tirzepatide concentrations were achieved following 4 weeks of once weekly administration." [6]
Zepbound® (tirzepatide) "The elimination half-life is approximately 5-6 days in patients with overweight or obesity" "the median time (range) to maximum plasma concentration of tirzepatide is 24 hours (8 to 72 hours)." [7]
Saxenda® (liraglutide) "an elimination half-life of approximately 13 hours, making liraglutide suitable for once daily administration" "maximum concentrations of liraglutide are achieved at 11 hours post dosing." [8]
  • Xinermei® (mazdutide) is also in Dosia's catalog. It has no FDA label. Dosia's mazdutide estimates use published early clinical data from a small Phase 1b study in Chinese adults with overweight or obesity [9], so they are lower confidence than estimates for FDA-labeled medications. No half-life figure is shown here.
  • Compounded products are not FDA-approved and have no FDA label. Dosia models them with the parameters of the matching branded active ingredient (for example, semaglutide or tirzepatide). Real compounded products may behave differently.
  • Labels are updated over time. Re-check the figures at each page review (label versions used: Ozempic v20, effective 2026-06-01; Wegovy v19, 2026-06-18; Rybelsus v14, 2026-01-30; Mounjaro v40, 2026-08-27; Zepbound v40, 2026-08-28; Saxenda v22, 2026-02-25).

How Dosia turns your log into an estimated curve

Dosia uses a standard textbook approach from pharmacokinetics [1][2]. In plain language:

  1. One "compartment". The model treats the body as a single well-mixed space. This is a deliberate simplification.
  2. Absorption. After each dose you log, the modeled amount rises toward a peak. How fast it rises is set from the time-to-peak (Tmax) reported for that medication.
  3. Elimination. The amount then declines at a steady proportional rate set by the published half-life (first-order elimination).
  4. Adding doses up. When doses of the same medication overlap, their curves are added together (superposition). This is why a regular schedule builds up toward a repeating pattern of peaks and troughs.
  5. What the number means. Dosia shows the estimated amount of medication remaining in the body, in mg. This is not a blood concentration, not a lab value, and not a measure of effect.
  6. One ingredient at a time. Different active ingredients are never added together. Each is shown as its own estimate.

Where the parameters come from, and how confident we are

The medications named below are examples; Dosia's catalog includes others.

Medication type Parameter source Confidence
FDA-approved medications (for example Ozempic®, Wegovy®, Mounjaro®, Zepbound®, Saxenda®) FDA prescribing information (table above) Highest of the set, but still population averages
Oral semaglutide (for example Rybelsus® and semaglutide tablets) FDA label half-life plus a low bioavailability factor. The label reports that only a very small fraction of an oral dose (roughly 0.4% to 2%, depending on the tablet product) reaches the bloodstream [5]. Medium: oral absorption varies a lot
Medications approved only outside the US (for example Xinermei® (mazdutide), 先维盈® (ecnoglutide)) Published clinical data (mazdutide: [9]) Low
Compounded products Parameters of the matching branded ingredient Low to medium: real products may differ
Illustrative chart: a modeled medication level rises after each dose, declines by half-life, and builds toward a steady pattern. Not real data. Time (half-lives) Estimated relative level (illustrative)
Illustrative only. Not real patient data and not specific to any medication or dose. Your actual blood levels can differ.

Why an estimate can differ from your real blood level

  • Population averages. Label half-lives describe averages from clinical studies. Individuals differ; for example, the Zepbound label reports between-person variability in clearance (CV% ~20%). [7]
  • Absorption varies. Labels report a range of times to peak (for example, 8 to 72 hours for tirzepatide). [6] Oral semaglutide absorption is very low and depends on how the tablet is taken. [5]
  • Simplified model. A one-compartment model is a simplification of how the body handles a drug.
  • Your body. Body size, other health conditions and other medicines can affect how a drug is distributed and cleared. [2]
  • Your log. An estimate is only as accurate as the doses and times you record. A missed or wrong entry changes the curve.
  • No measurement. Dosia never measures anything in your body. Only a laboratory test can measure a drug concentration.

What estimates are for, and what they are not for

Good uses

  • Seeing your logged doses on a timeline
  • Noticing how your own notes, such as side effects, line up with your dose schedule
  • Bringing a clear record to your appointment

Not for

  • Deciding whether, when or how much to dose
  • Deciding what to do after a missed or late dose
  • Switching or combining medications
  • Judging whether a medication is "working"

For any of these, talk to your prescriber and follow the official prescribing information.

FAQ

What is a GLP-1 medication-level estimate?

It is a modeled curve that shows how the amount of a GLP-1 medication in the body might rise and fall over time. It is calculated from your logged doses and the medication's published half-life. It is an estimate, not a measurement.

Is the medication level in Dosia my blood level?

No. Dosia shows a model-based estimate of the amount of medication remaining in the body, in mg. It is not a measured blood concentration, and your real levels can differ.

What is the half-life of semaglutide?

FDA labels for Ozempic, Wegovy and Rybelsus state an elimination half-life of approximately 1 week for semaglutide.

What is the half-life of tirzepatide?

The FDA label for Mounjaro states an elimination half-life of approximately 5 days. The Zepbound label states approximately 5–6 days in patients with overweight or obesity.

Why does my estimated level build up over the first weeks?

With regular dosing, each new dose adds to what remains from earlier doses, so levels build up until intake and elimination balance. For semaglutide, the Ozempic label says steady-state exposure is reached after 4 to 5 weeks of once-weekly dosing.

Can I use the estimate to adjust my dose or decide about a missed dose?

No. Estimates are for informational tracking only and must not be used for dosing or treatment decisions. Ask your prescriber and follow your medication's prescribing information.

Where do Dosia's half-life figures come from?

For medications approved by the US FDA, Dosia uses parameters from the FDA prescribing information; the figures on this page are quoted from DailyMed. For medications approved only outside the US, such as Xinermei® (mazdutide) and 先维盈® (ecnoglutide), Dosia uses published clinical data, and those estimates are lower confidence. Compounded products use the parameters of the matching branded ingredient and may differ in reality.

Sources

  1. Hallare J, Gerriets V. Elimination Half-Life of Drugs. StatPearls, NCBI Bookshelf (NIH/NLM). https://www.ncbi.nlm.nih.gov/books/NBK554498/
  2. Grogan S, Preuss CV. Pharmacokinetics. StatPearls, NCBI Bookshelf (NIH/NLM). https://www.ncbi.nlm.nih.gov/books/NBK557744/
  3. OZEMPIC (semaglutide) injection — Prescribing Information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=adec4fd2-6858-4c99-91d4-531f5f2a2d79
  4. WEGOVY (semaglutide) — Prescribing Information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ee06186f-2aa3-4990-a760-757579d8f77b
  5. RYBELSUS (oral semaglutide) tablets — Prescribing Information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=27f15fac-7d98-4114-a2ec-92494a91da98
  6. MOUNJARO (tirzepatide) — Prescribing Information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d2d7da5d-ad07-4228-955f-cf7e355c8cc0
  7. ZEPBOUND (tirzepatide) — Prescribing Information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=487cd7e7-434c-4925-99fa-aa80b1cc776b
  8. SAXENDA (liraglutide) — Prescribing Information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3946d389-0926-4f77-a708-0acb8153b143
  9. Ji L, et al. Safety and efficacy of a GLP-1 and glucagon receptor dual agonist mazdutide (IBI362) 9 mg and 10 mg in Chinese adults with overweight or obesity: a randomised, placebo-controlled, multiple-ascending-dose phase 1b trial. eClinicalMedicine, 2022. PMC9561728. https://pmc.ncbi.nlm.nih.gov/articles/PMC9561728/

Last reviewed: 2026-10-18. Label figures checked against DailyMed on that date. Dosia is a tracking tool, not a medical provider. Not medical advice.

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