Written and fact-checked to our published editorial standards.Last updated 2026-08-21. Every clinical claim on this page is sourced to a named primary authority, listed at the foot of the page — see how we research, source, and correct our work.
Direct answer
What you need to know
Evidence strength: Strong
“How long” is three different questions, and the class has no single answer to any of them. How long until it works: no label states one, and only 3 of 9 state even when blood levels plateau. How long it stays in you: from 2.4 hours for Byetta to approximately 1 week for Wegovy, a range of more than a hundredfold. How long out of the fridge: 5 different allowances — 14, 21, 28, 30 and 56 days.
Key takeaways
The out-of-fridge limit is not a class property. Applying one product’s number to another can put you weeks past it.
Rybelsus needs no refrigeration at all, which the storage conversation almost never mentions.
No approved label states a time until the medication starts working. A page that gives you one is not reading from the label.
Semaglutide is present in circulation for about five to seven weeks after the last injection, which is why pregnancy planning starts months ahead.
Important limitation: These are label figures for approved products. Compounded preparations are not covered by any of them: nobody has reviewed a compounded vial’s stability, so its storage instructions come from the pharmacy that made it and from nowhere else.
Next action: Find your own product below rather than reading the class row. If the question behind yours is really “why does it not feel like it is working”, the titration tracker answers that one, because the early doses are not treatment doses.
General education, not medical advice. Your own product's label and your prescriber are the authority on storage and on timing.
How long until it works
This is the most-asked version of the question and the one with the least satisfying answer, because no approved label states a time until the drug starts working. Onset of appetite effect is not something the labels quantify, and a page that gives you “two to four weeks” has taken it from somewhere other than the prescribing information.
What some labels do state is when blood levels plateau, which is a different fact. 3 of the 9 products here say so: Zepbound, Mounjaro, Trulicity. Tirzepatide’s reaches steady state after four weeks of once-weekly dosing. Semaglutide’s label does not give a steady-state time at all, despite the molecule having the longest half-life in the class — so for the most-prescribed drug here, the honest answer is that the label does not say.
There is a better explanation for the experience behind the question. The dose you start on is not the dose the published results were measured at. Every product in this class escalates over weeks, and the label wording is explicit that the early steps are initiation and escalation rather than treatment. Someone four weeks in comparing themselves to a trial headline is comparing themselves to a dose they have not reached. That is what the week-by-week escalation tracker is built to show.
How long it stays in your system
Here the labels are precise, and the spread across the class is enormous — from 2.4 hours to approximately 1 week, which is more than a hundredfold. That is the difference between a drug you take twice a day and one you take once a week, and it is also what decides how long a decision to stop takes to take effect.
Elimination half-life and washout as each product’s FDA-approved label states them, longest-acting first. Where a label does not state how long the drug remains in circulation, that is marked rather than calculated from the half-life. Read 2026-08-21.
The five-to-seven-week figure for semaglutide is the one with the largest practical consequence, and it is not about weight. It is why the Wegovy prescribing information advises discontinuing at least two months before a planned pregnancy — the drug is still circulating long after the last injection. That, and the rest of what the labels say about pregnancy and contraception, is on the interactions page.
How long it can be out of the fridge
This is the question where a wrong answer costs something, and it is the one most often answered as though the class had a single rule. It does not. The labels give 5 different allowances — 14, 21, 28, 30, 56 days — and for several products the limit changes depending on whether the pen has been used yet. Two products from the same manufacturer, containing the same molecule, can carry different numbers.
Refrigeration and out-of-refrigeration limits from each product’s own label. The condition column is not a footnote: for most of these the allowance only applies under it. Read 2026-08-21. Your product’s own label is the authority.
single-dose pen or syringe, before the cap is removed, at 8°C to 30°C — the single-patient-use FlexTouch pen is a different rule: 56 days after first use
after first use, at a temperature not exceeding 25°C, and discarded 30 days after first use even if drug remains
Fourteen days for one product and fifty-six for another, from labels that sit side by side in the same drug class. “About a month” is wrong in both directions.
The tablets are not in this conversation at all
Every discussion of GLP-1 storage is conducted in terms of pens, cool bags and hotel minibars, because until recently every GLP-1 was an injection. Rybelsus is stored at room temperature between 68°F and 77°F throughout, with no refrigeration step at any point.
For anyone whose real question is about travelling, that is the most useful fact on this page, and it belongs alongside the other reason the oral route keeps turning out to be the practical one: it is also the cheapest approved form of semaglutide. What the tablets ask in return is a fasting routine every morning, which is set out on the GLP-1 pill page.
What none of this covers
Every figure on this page comes from an FDA-approved label, which means none of it applies to a compounded preparation. A compounded vial’s stability has not been reviewed by anyone, its concentration may differ from any approved product, and its storage instructions come from the pharmacy that made it. Using an approved product’s out-of-fridge allowance for a compounded vial is applying a number from a document that was never about it. What compounding is, and what it is not, is on the compounded guide.
Common questions
How long does it take for a GLP-1 to work?
No approved label states a time until it starts working, and any page giving you one is not reading from the label. What some labels do state is when blood levels plateau: tirzepatide's says four weeks of once-weekly dosing. Semaglutide's does not say. Separately, the dose you start on is not the dose the published results were measured at — you climb for weeks before reaching it, which is usually the real answer to why it does not feel like it is working yet.
How long does a GLP-1 stay in your system?
It depends heavily on which one. Semaglutide's half-life is about a week, and the Wegovy label states the drug is present in circulation for about five to seven weeks after the last injection. Exenatide's half-life is 2.4 hours. Between those two extremes are tirzepatide and dulaglutide at around five days and liraglutide at 13 hours — a range of more than a hundredfold across one drug class.
How long can a GLP-1 be out of the fridge?
There is no class answer, and this is the question where guessing costs you. The approved labels give five different allowances — 14, 21, 28, 30 and 56 days — and for several products the limit depends on whether the pen has been used yet. Rybelsus is not refrigerated at all. Read your own product's label rather than a figure you saw for a different one.
Does a GLP-1 expire?
Every product carries an expiry date on its own label, and separately a limit on how long it may spend outside the refrigerator, which is usually the shorter of the two once a pen is in use. Several labels say to discard the pen a set number of days after first use even if medication remains in it.
Do you have to refrigerate a GLP-1?
Not all of them. The oral products are stored at room temperature between 68°F and 77°F throughout and have no refrigeration step at all. Every injectable in this class is refrigerated before use, with a limited allowance for time spent out.
Sources
Each source below supports specific statements on this page. We cite the strongest available authority and verify against the current version before publishing.
FDA-approved prescribing information (drug labels)DailyMed, U.S. National Library of MedicineSupports: Elimination half-life, steady-state statements and storage sections read from the FDA-approved prescribing information for all 9 products named. Verified 2026-08-21.
This page is general education, not medical advice. Talk to your own healthcare provider about your situation before starting, stopping, or changing any medication.