How Long Semaglutide Stays Good in Your Refrigerator

Semaglutide lasts up to 30 days once opened and stored in the refrigerator

Semaglutide — the injectable medication sold as Ozempic, Wegovy, or Mounjaro — remains safe to use for 30 days after you first open the pen or vial, as long as you keep it refrigerated between 36°F and 46°F (2°C to 8°C). Once that 30-day window closes, you should discard the pen or vial, even if it looks and feels normal. The medication degrades over time, and using it past this point means you cannot be certain of the dose you are actually receiving.

The 30-day clock starts the moment you puncture the pen or vial for the first injection — not the date you received it from the pharmacy. If your pen arrives and sits unopened in the refrigerator for two weeks before you use it, you still have 30 days from the day you take that first dose. This matters because many people assume the expiration date on the box is what counts, but for injectable medications, the opened-vial rule overrides the printed date.

Key Takeaways

• An opened semaglutide pen or vial is good for exactly 30 days when stored in a refrigerator set between 36°F and 46°F.
• The 30-day countdown begins the moment you use the pen for the first injection, not when you receive it from the pharmacy.
• Unopened pens and vials can stay in the refrigerator until the printed expiration date, which is usually one to two years away.
• If your pen has been left at room temperature for more than 30 minutes, or if it has been frozen, do not use it — discard it safely and contact your pharmacy for a replacement.
• Write the date you open each pen directly on the label so you know exactly when the 30-day window closes.

Why the 30-day limit matters for your dose

Semaglutide is a peptide — a chain of amino acids that your body recognizes and uses to regulate blood sugar and appetite. Peptides are fragile molecules. Over time, especially in a liquid or suspension, they break down into smaller pieces that no longer work the way they should. After 30 days in the refrigerator, enough of the active ingredient has degraded that the pen no longer delivers a reliable dose.

This is not a safety issue in the sense that the medication becomes poisonous. Rather, it becomes unreliable. You might inject what you think is your full weekly dose, but if the medication has degraded, you could be getting 80 percent of the dose, or 60 percent, or something in between. That unpredictability can affect your blood sugar control or your appetite suppression, and it defeats the purpose of taking the medication at all.

The 30-day window is set by the manufacturer based on real-world testing. Novo Nordisk, which makes Ozempic and Wegovy, tested how long the medication stays stable under normal refrigerator conditions and set the limit conservatively — meaning the actual medication may remain somewhat stable a bit longer, but 30 days is the point at which they can no longer may provide the dose.

Storage conditions that extend or shorten the 30 days

The 30-day window assumes your refrigerator stays between 36°F and 46°F at all times. If your fridge runs warmer or colder than that, the medication degrades faster or slower. A refrigerator that drifts to 50°F will shorten the usable life. A freezer, by contrast, will destroy the medication immediately — semaglutide cannot be frozen, and a frozen pen is no longer safe to use.

Room temperature (around 68°F to 77°F) is acceptable for a short time — up to 30 minutes — if you are traveling or need to carry the pen with you. Beyond 30 minutes at room temperature, the medication begins to degrade noticeably. If your pen has sat on a counter or in a warm car for more than 30 minutes, mark it as unusable and contact your pharmacy for a replacement.

Once a pen has been at room temperature, even if you put it back in the refrigerator, the 30-day countdown does not reset. The damage is already done. So if you accidentally left your pen out for 20 minutes, then refrigerated it, you still have only 30 days from the day you first opened it — not 30 days from when you put it back in the fridge.

How to track your 30-day window

The simplest method is to write the date you first use the pen directly on the label with a permanent marker. Use the format MM/DD so there is no confusion. For example, if you open your pen on January 15th, write "01/15" on the label. Then, 30 days later on February 14th, discard the pen even if there is medication left inside.

If you use your semaglutide once a week, you will get roughly four injections from each pen before the 30-day window closes. If you use it twice a week, you will get about two injections. The number of doses does not matter — only the calendar days matter. Once 30 days have passed, the pen is done.

Keep a small calendar or phone reminder set for 28 days after you open each pen. This gives you a two-day buffer to order a replacement from your pharmacy before your current pen expires. Many people find it helpful to order their next pen as soon as they open the current one, so there is no gap in their supply.

What to do with an expired or damaged pen

Do not throw a used semaglutide pen in the household trash. Needles and medication containers require special disposal. Most pharmacies have a medication take-back program — you can bring your expired or damaged pens to the pharmacy counter, and they will dispose of them safely at no cost. Some areas also have community drug take-back days or mail-back programs.

If your pen has been frozen, left at room temperature for more than 30 minutes, or has passed the 30-day mark, do not attempt to use it. The risk of an unreliable dose is not worth the cost of the medication. Contact your pharmacy and explain what happened — they may be able to issue a replacement, especially if the damage was due to a shipping or storage error on their end.

Never reuse a needle or attempt to refill a pen. Semaglutide pens are single-use devices. Once the medication is gone or the pen has expired, the entire pen must be discarded.

Unopened pens and long-term storage

An unopened semaglutide pen can stay in the refrigerator until the expiration date printed on the box, which is typically one to two years from the date you receive it. You do not need to use it within 30 days if you have not opened it yet. This means you can safely stock up or keep a backup pen on hand without worrying about it going bad.

However, unopened pens should still be stored in the refrigerator, not at room temperature. If an unopened pen is left at room temperature for an extended period — say, several hours or a full day — it may begin to degrade. When in doubt, refrigerate it.

If you receive an unopened pen and the box does not have an expiration date printed on it, check the pen itself — the date is usually stamped on the barrel or the label. If you cannot find an expiration date, contact your pharmacy and ask.

Frequently Asked Questions

Can I use my semaglutide pen after 30 days if it still has medication in it?

No. The 30-day limit is firm, regardless of how much medication remains in the pen. After 30 days, the active ingredient has degraded enough that the dose is no longer reliable. Discard the pen and use a fresh one.

What if I forgot to write the date on my pen and do not remember when I opened it?

If you cannot remember the exact date, mark the pen as expired and discard it. It is not worth the risk of an unreliable dose. Going forward, write the date on every pen the moment you open it — use a permanent marker on the label.

Does my refrigerator temperature affect how long the pen lasts?

Yes. The 30-day window assumes your fridge stays between 36°F and 46°F. If your fridge is warmer, the medication degrades faster. If it is colder (but not frozen), it may last slightly longer, but 30 days is still the safe limit. Check your fridge temperature with a thermometer if you are unsure.

Is it okay to leave my semaglutide pen on the counter while I prepare my injection?

Yes, for a few minutes. You can safely leave the pen at room temperature for up to 30 minutes total. If you are taking your time to prepare the injection, that is fine. Just do not leave it out for longer than that, and put it back in the refrigerator as soon as you are done.

What should I do if my pen was accidentally frozen?

Do not use it. Freezing damages the medication permanently. Discard the pen and contact your pharmacy for a replacement. If the pen was frozen due to a shipping error, the pharmacy may replace it at no cost.