Dulaglutide half-life, time to peak and level curve
Dulaglutide has an elimination half-life of about 5 days, and its FDA label puts the peak 24 to 72 hours after an injection at steady state, with a median of 48. Peptrend's preset uses 5 days and 48 hours. In the app's model one dose climbs to 75.8% of the logged amount at 48 hours, and 42.7% is left a week later. Repeated weekly, the level settles within 20 to 25 days, between 129.6% and 68.7% of one dose.
The preset's numbers, beside its source
What the Dulaglutide preset writes into Settings › Medication, beside what the FDA label says. The sources at the foot of the page name what the app itself cites.
| Constant | Peptrend preset | FDA label |
|---|---|---|
| Half-life | 5 days | Approximately 5 days |
| Time to peak (Tmax) | 48 hours | 24 to 72 hours at steady state, median 48 |
| Bioavailability | 100%, every logged milligram | 65% and 47% at the two single doses tested |
| Dosing interval | Every 7 days | Once weekly |
| Time to steady state | 20 to 25 days (4 to 5 half-lives) | Between 2 and 4 weeks of once-weekly dosing |
The curve the model draws
Both curves are Peptrend's own model run on the four numbers above and scaled to one logged dose, so they carry no dose amount. Each point is a decayed-milligram estimate built from a published half-life and time to peak. The model has no volume of distribution, so it cannot give a blood or plasma concentration. The curves describe dulaglutide as this preset models it, and describe no effect of the app and no person's result.
| Model quantity | Value for this preset |
|---|---|
| Elimination rate, ke = ln 2 ÷ half-life | 0.1386 per day |
| Absorption rate, ka, solved from Tmax | 1.23 per day |
| One dose at its peak | 75.8% of the logged dose, at 48 hours |
| One dose, one interval later | 42.7% of the logged dose |
| Accumulation ratio, 1 ÷ (1 − e^(−ke·τ)) | 1.61× |
| Settled peak and trough | 129.6% and 68.7% of one logged dose |
What does the label say about dulaglutide’s half-life and peak?
Dulaglutide, sold as Trulicity, has an elimination half-life of approximately 5 days, by the prescribing information Peptrend cites. The label puts the time to maximum plasma concentration at steady state between 24 and 72 hours, with a median of 48, and reports steady-state concentrations between 2 and 4 weeks into once-weekly dosing. Its absolute bioavailability depends on the dose: 65% and 47% at the two single doses tested.
The preset takes the label’s median of 48 hours and its 5-day half-life, which is also the half-life of the tirzepatide preset. The two differ only in the time to peak, so they make a clean test of what Tmax alone does to a curve.
What does one dose look like in the model?
One dose climbs for two days and turns over at 75.8% of the logged amount. That is lower than the tirzepatide preset’s peak on the same half-life, and the whole difference is the extra day of climbing. A peak at 48 hours arrives with two days of elimination spent, so it lands at 2^(−48 ÷ 120) of the dose, 120 hours being the half-life.
The slower absorption also holds the level up later in the week. The absorption rate the app solves from 48 hours is about 1.23 per day, an absorption half-life near 13.5 hours, and a week after the injection 42.7% is left, a little more than tirzepatide keeps at the same point. Reading the absorption curve shows how Tmax and the half-life split that work.
What happens when weekly doses repeat?
The level settles within four to five half-lives, 20 to 25 days, between 129.6% of one logged dose at its highest and 68.7% just before the next injection. The label’s own figure is 2 to 4 weeks.
The label also offers a second check on the model. It reports an accumulation ratio of approximately 1.56 once dulaglutide reaches steady state. A one-compartment model with a 5-day half-life and a weekly interval gives 1 ÷ (1 − e^(−ke·7)) = 1.61. The two agree to within about 3%, which is as close as a single half-life applied to every dose could reasonably be expected to come. How long a GLP-1 takes to reach steady state derives that ratio.
Where does the model part from the label?
- Bioavailability. The label’s figures are 65% and 47%, and the model uses 100%. That puts the curve between about 1.5 and 2.1 times as high as the label’s figures would, the largest gap of the injection presets. Because the label’s figure changes with the dose, a titration logged in the app is scaled by one constant where the label implies two.
- Time to peak. The label’s 24 to 72 hours was measured at steady state. The model uses the same 48 hours for the first dose as for the tenth.
- People differ. The half-life is a population figure, and nothing in the app measures how fast any one person clears the drug.
Every constant is editable in Settings › Medication, and the app asks before a preset overwrites them.
How Peptrend logs dulaglutide
With the Dulaglutide preset applied from Use a preset in Settings › Medication, each shot logged on the Shots tab carries a date and time and a dose in milligrams, with the injection site, vial and pain score optional. The model above runs over every taken dose logged under the name Dulaglutide.
The arithmetic behind these curves
- How long until a GLP-1 reaches steady state? Four to five half-lives
- When does a GLP-1 peak after injection? Tmax and the absorption curve
- Does oral semaglutide have the same half-life as the injection?
- Every medication preset, side by side
Other presets: Semaglutide (injection) · Semaglutide (tablet) · Tirzepatide · Liraglutide · Orforglipron
Sources
- TRULICITY (dulaglutide) injection — prescribing information, section 12.3 (revised 3/2026), DailyMed — FDA label, cited in the app
- Min JS et al. A Comprehensive Review on the Pharmacokinetics and Drug-Drug Interactions of Approved GLP-1 Receptor Agonists and a Dual GLP-1/GIP Receptor Agonist. Drug Design, Development and Therapy, 2025 — Review, cited in the app
- Wadhwa RR, Cascella M. Steady State Concentration. StatPearls, NCBI Bookshelf