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Wegovy® half-life calculator

Wegovy® contains semaglutide, and its US label gives an elimination half-life of about one week. That value is filled in below and you can change it. Add the dose and schedule from your prescription to see an estimated curve.

Updated

Label value: about 7 days (Wegovy® US label). Change it if your clinician gives you a different value.

days
Highest point
–
Left before the last dose
–
Left a week after the last dose
–

Fill in the half-life, dose and interval to draw the curve.

Calculated in your browser. Nothing is sent.

Simple exponential decay from the numbers you enter. It is not a blood level and not medical advice. The dose and schedule come only from your prescription; PepLabo never suggests a dose.

The formula this calculator uses

  1. One dose

    remaining = dose × 0.5^(time elapsed ÷ 7 days). A half-life entered in hours is divided by 24 to work in days.

  2. Repeated doses

    Each dose fades on its own; the curve is the sum of every dose given up to that moment (up to 60 doses).

  3. Three outputs

    Highest point = the largest total at the dose moments · left before the last dose = the total just before the last dose (blank for a single dose) · left a week after = the total 7 days after the last dose.

  4. Levelling off

    With a fixed dose and interval, peak ≈ one dose × 1 ÷ (1 − 0.5^(interval ÷ half-life)); it settles after about 4 to 5 half-lives.

Worked example

Half-life 7 days: whatever its size, a single dose has 50% left after one half-life, 25% after two and about 3% after five. Repeated at the label’s 7-day interval, the peak levels off at about 2 times one dose: 1 ÷ (1 − 0.5^(7 ÷ 7)) = 2.

Worked examples

The dose field was set to 1: not a dose, just a way to read results as multiples of one dose. Each row was entered into this calculator and the result copied as shown.

Half-life 7 days, dose 1 (no unit), interval 7 days
EntryHighest pointLeft before the last doseLeft a week after the last dose
1 dose1–0.5
10 doses, once weekly211

How much of one dose is left

Share of one dose left with a half-life of 7 days
Time elapsedHalf-livesLeft
0 days0100%
7 days150%
14 days225%
21 days312.5%
28 days46.3%
35 days53.1%

Plain arithmetic: left = 0.5^(number of half-lives).

What the Wegovy® label says

  • Elimination half-life of semaglutide: about 1 week [1].
  • Present in the circulation for about 5 to 7 weeks after the last injection [1].
  • Stop at least 2 months before a planned pregnancy, because of the long half-life [1].
  • Injection once weekly; tablet once daily, on an empty stomach in the morning [1].

What this calculator does not do

  • It does not suggest a dose, a schedule, starting, stopping or switching medication.
  • It does not show a blood level; it does not model absorption, time to peak or personal differences.
  • It does not decide anything about a missed dose; it quotes the label’s rule below, and the decision is your prescriber’s.
  • It does not tell you when a medicine is "gone" or when to switch to another one.

About this estimate and your privacy

The half-life comes from the label [1]; the dose, interval and number of doses are only what you enter. The model counts each dose as fully present the moment it is given, while a real injection is absorbed over time, which is why the curve steps straight up at each dose.

Everything is worked out by a script inside this page. The script makes no network requests, the page’s security policy (Content-Security-Policy with default-src none and no connect-src) would block them anyway, and nothing you type is stored, not even in your browser’s storage. Reload the page and the fields are empty again.

Next to each source below is what it supports on this page.

Wegovy® is a trademark of Novo Nordisk A/S. PepLabo is not affiliated with or endorsed by Novo Nordisk.

Questions

How long does Wegovy® stay in your system?

The US label says about 5 to 7 weeks after the last injection [1]. That is in line with about five half-lives of one week each.

Can I use this for the Wegovy® tablet?

Yes. The half-life is that of semaglutide either way [1]; enter 1 day as the interval for a once-daily tablet. How the tablet is absorbed is not part of this simple model.

What does the label say about a missed dose?

Wegovy®: for the injection, if the next scheduled dose is more than 2 days (48 hours) away, take the missed dose as soon as possible; if it is less than 2 days away, skip it. If 2 or more weekly doses in a row are missed, contact the prescriber about restarting. A missed tablet is skipped and the next one taken the following day. [1] Your own prescriber’s instructions always come first; this calculator does not decide anything about a missed dose.

Why does the label mention stopping before a pregnancy?

Because of the long half-life: Wegovy®: stop at least 2 months before a planned pregnancy because of the long half-life of semaglutide. [1] Talk to your prescriber about pregnancy plans.

Is there anything to know before a planned surgery?

The labels say these medicines can slow stomach emptying, that rare cases of pulmonary aspiration have been reported during procedures under general anaesthesia or deep sedation, and that you should tell your healthcare providers you take it before any planned surgery or procedure [1].

Why do vomiting or diarrhoea matter?

The labels note that nausea, vomiting or diarrhoea can lead to dehydration, which has been linked to acute kidney injury [1]. If you cannot keep fluids down, contact your prescriber.

Why is the dose field empty?

PepLabo never suggests a dose. Enter the dose and schedule from your prescription; the calculator only draws how they add up and fade over time. Any unit works: enter mg and the results are in mg.

Is this curve my blood level?

No. It is a simple model based only on the half-life; it ignores absorption, time to peak, body weight, kidney function and other personal factors.

How is this different from the curve in the PepLabo app?

The app’s Today screen uses a simplified one-compartment model (Bateman) with the half-life and time to peak, scaled to the highest point in the window, so it shows a relative trend rather than an amount. This page skips absorption and shows absolute totals in the unit you enter.

Sources

Sources checked on

  1. Wegovy® (semaglutide) injection and tablets: US prescribing information, Novo Nordisk (DailyMed) Supports: elimination half-life of about 1 week; about 5 to 7 weeks in circulation after the last injection; missed-dose rules for injection and tablets; stopping 2 months before a planned pregnancy; tablets once daily; surgery and dehydration warnings.

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