Half-Life Visualizer
See how a drug’s modeled level rises, falls and builds up over repeated doses, using the half-life and time to peak from its US label. Overlay up to 3 compounds.
Modeled Amount in the Body Over Time
Understanding this chart
Each curve is a one-compartment model with first-order absorption: after every dose the modeled amount rises to a peak, then falls by half every half-life, and repeated doses add together until the amount lost between doses equals the amount given. Half-lives and times to peak come from each drug’s US label. The model assumes the whole dose is absorbed, so the vertical axis is an amount in the body, not a blood level, and it says nothing about how long an effect lasts. How the model works and where its numbers come from.
What the chart draws
Each curve is the simplest model that has both an absorption phase and an elimination phase: one compartment with first-order absorption. After a single dose D, the modeled amount at time t is
A(t) = D · ka / (ka − ke) · (e−ket − e−kat)
where ke = ln 2 ÷ half-life is the elimination rate. The absorption rate ka is not published on labels, so the tool solves for it: it picks the ka at which a single dose peaks exactly at the label's time to peak, using tmax = ln(ka/ke) ÷ (ka − ke). Repeated doses are added together, starting from the first dose at time zero, so the chart shows the build-up as well as the plateau.
The vertical axis is an amount in the body in the dose's own units, calculated as if the whole dose were absorbed. It is not a blood concentration: turning an amount into nanograms per millilitre needs a volume of distribution and the fraction absorbed, and the chart's purpose is to show shape and timing, not levels. The label bioavailability is shown beside each compound for context but is not applied.
Where each curve's numbers come from
The tool draws only compounds whose half-life and time to peak are both stated in a current US label, and each half-life must match the one in our encyclopedia entry or the page will not build. Where a label gives a range, the tool uses its midpoint and says so. The default dose and interval for each compound are the label's starting dose and interval.
| Compound | Label | Half-life; time to peak | Bioavailability | Label interval | Modeled accumulation | Source |
|---|---|---|---|---|---|---|
| Semaglutide | Ozempic / Wegovy injection | about 1 week; peak 1–3 days (midpoint 2) | 89% | weekly | 2.00 | 1 |
| Tirzepatide | Mounjaro / Zepbound | about 5 days; peak 8–72 h (midpoint 40) | 80% | weekly | 1.61 | 2 |
| Dulaglutide | Trulicity | about 5 days; peak 24–72 h (median 48) | 65% at 0.75 mg | weekly | 1.61 | 3 |
| Liraglutide | Victoza / Saxenda | about 13 h; peak 8–12 h (midpoint 10) | 55% | daily | 1.39 | 4 |
| Exenatide | Byetta | 2.4 h; median peak 2.1 h | not stated | every 12 h | 1.03 | 5 |
| Orforglipron (oral) | Foundayo | 29–49 h (midpoint 39); peak 4–8 h (midpoint 6) | 77% at 0.8 mg | daily | 2.88 | 6 |
| PT-141 (bremelanotide) | Vyleesi | 2.7 h (1.9–4.0); median peak 1.0 h | about 100% | weekly | 1.00 | 7 |
| Tesamorelin | EGRIFTA SV | 8 min (EGRIFTA SV); median peak 0.15 h | under 4% | daily | 1.00 | 8 |
The last column is the model's accumulation ratio at steady state, 1 ÷ (1 − 2−interval/half-life): how much higher the plateau peak sits than the peak after the first dose. It gives a check against a measured value. Trulicity's label reports an accumulation ratio of about 1.56 at steady state;3 the model, from the label's 5-day half-life and weekly dosing, gives 1.61.
Build-up, plateau and washout
With repeated doses, each new dose lands on what is left of the previous ones, and the level climbs until the amount eliminated between doses equals the dose. The time this takes depends only on the half-life: after one half-life the level has covered half the distance to its plateau, after four about 94%, after five about 97%. The labels show the same thing in their own numbers. Semaglutide, with a half-life of about a week, reaches steady state after 4 to 5 weeks of weekly dosing and stays in the circulation for about 5 weeks after the last dose.1 Tirzepatide reaches steady state after 4 weeks.2 Orforglipron, with a half-life of 29 to 49 hours, gets there in about a week of daily tablets.6
The same arithmetic explains why a missed dose of a long-acting drug changes little, and why a short-acting one behaves differently: exenatide's 2.4-hour half-life means it is measurable for about 10 hours after a dose,5 so twice-daily dosing gives peaks and near-empty troughs rather than a plateau. Doubling a dose does not double how long a drug lasts: it adds one half-life.
Why most peptides are not on the list
The previous version of this tool drew curves for BPC-157, TB-500, MOTS-c, epithalon, GHK-Cu, AOD-9604 and others, using half-lives that no human study reports. Our encyclopedia entries for these compounds list their human half-life as undetermined or not measured, and a curve built on an invented number would teach the wrong thing with a precise-looking picture. They are not drawn.
Three compounds have a human half-life but not the second number the model needs. CJC-1295 with DAC has an estimated half-life of 5.8 to 8.1 days after injection under the skin, but its published abstract gives no time to peak.9 Retatrutide's half-life is about 6 days, from a phase 1b trial whose abstract likewise gives no time to peak.10 Ipamorelin's 2-hour half-life was measured only after an intravenous infusion, so it says nothing about an injection under the skin.11 When a label or a paper supplies the missing number, the compound can be added.
What the model leaves out
Effects do not follow the curve. Tesamorelin's half-life is 8 minutes and under 4% of an injected dose reaches the circulation,8 yet it is taken once daily because what matters is the growth hormone and IGF-1 response it sets off, which lasts far longer than the drug. Ipamorelin produced a single pulse of growth hormone that peaked at about 40 minutes and then fell to negligible levels,11 a response the drug's own half-life does not describe.
Slow absorption can masquerade as a long half-life. When a drug is absorbed more slowly than it is eliminated, as with many depot injections and implants, the decline after the peak reflects absorption, not elimination. This is called flip-flop kinetics, and reading such a curve as an elimination half-life overstates how long the drug stays once it is absorbed.12 The model assumes absorption is faster than elimination, which holds for every compound listed here.
People differ. Labels report averages, often with wide ranges: bremelanotide's half-life runs from 1.9 to 4.0 hours.7 Kidney function, body size, injection site and the product itself all shift the real curve. Treat the chart as a picture of how half-life and dosing interval interact, not as a prediction for any person.
Sources
- Novo Nordisk. OZEMPIC (semaglutide) injection, US prescribing information, section 12.3: absolute bioavailability 89%; maximum concentration 1 to 3 days post dose; steady state after 4 to 5 weeks of once-weekly administration; elimination half-life approximately 1 week, present in the circulation about 5 weeks after the last dose. DailyMed version of June 10, 2026, read September 30, 2026.
- Eli Lilly and Company. MOUNJARO (tirzepatide) injection, US prescribing information, section 12.3: steady state after 4 weeks of once-weekly administration; time to maximum concentration 8 to 72 hours; absolute bioavailability 80%; elimination half-life approximately 5 days. DailyMed version of September 2, 2026, read September 30, 2026.
- Eli Lilly and Company. TRULICITY (dulaglutide) injection, US prescribing information, section 12.3: time to maximum concentration 24 to 72 hours (median 48); accumulation ratio approximately 1.56; absolute bioavailability 65% (0.75 mg) and 47% (1.5 mg); elimination half-life approximately 5 days. DailyMed version of August 10, 2026, read September 30, 2026.
- Novo Nordisk. VICTOZA (liraglutide) injection, US prescribing information, section 12.3: maximum concentrations 8 to 12 hours post dosing; absolute bioavailability approximately 55%; elimination half-life approximately 13 hours. DailyMed version of November 17, 2025, read September 30, 2026.
- AstraZeneca. BYETTA (exenatide) injection, US prescribing information, section 12.3: median peak plasma concentration at 2.1 hours; mean terminal half-life 2.4 hours; measurable for approximately 10 hours post-dose. DailyMed version of September 8, 2025, read September 30, 2026.
- Eli Lilly and Company. FOUNDAYO (orforglipron) tablets, US prescribing information, section 12.3: steady state after approximately 1 week of once-daily dosing; maximum concentration 4 to 8 hours post dose; absolute bioavailability 77% after a 0.8 mg dose; elimination half-life approximately 29 to 49 hours. DailyMed version of August 13, 2026, read September 30, 2026.
- Cosette Pharmaceuticals. VYLEESI (bremelanotide) injection, US prescribing information, section 12.3: median Tmax approximately 1.0 hour (0.5 to 1.0); absolute bioavailability about 100%; mean terminal half-life approximately 2.7 hours (1.9 to 4.0). DailyMed version of November 18, 2025, read September 30, 2026.
- Theratechnologies Inc. EGRIFTA SV (tesamorelin) for injection, US prescribing information, section 12.3: absolute bioavailability less than 4%; median Tmax 0.15 h; mean elimination half-life 8 minutes after 1.4 mg. DailyMed version of July 31, 2026, read September 30, 2026.
- Teichman, S. L. et al. (2006). Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. Journal of Clinical Endocrinology and Metabolism, 91(3), 799-805. PMID: 16352683 · doi:10.1210/jc.2005-1536
- Urva, S. et al. (2022). LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial. Lancet, 400(10366), 1869-1881. PMID: 36354040 · doi:10.1016/S0140-6736(22)02033-5
- Gobburu, J. V. et al. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical Research, 16(9), 1412-1416. PMID: 10496658 · doi:10.1023/a:1018955126402
- Yáñez, J. A. et al. (2011). Flip-flop pharmacokinetics--delivering a reversal of disposition: challenges and opportunities during drug development. Therapeutic Delivery, 2(5), 643-672. PMID: 21837267 · doi:10.4155/tde.11.19
This explainer describes how the tool works and what its numbers rest on. It is not medical advice and does not recommend any dose or product.