The short answer
Follow your compounding pharmacy’s label for storage, mixing and the beyond-use date, because compounded products differ and are not FDA-approved. Keep vials cold, use a new sterile needle and syringe every dose, and never use a vial that arrived warm. FDA advises discarding a multi-dose vial 28 days after first use, even if the label allows longer. The biggest risk is dosing: mixing up units, milliliters and milligrams has put people in the hospital.
At GLP-1 SOS, many people who write to us use compounded semaglutide or tirzepatide from a vial, often after months on a branded pen. The pen measured for them; a vial and syringe do not, and instructions vary by pharmacy. Here is what FDA has said, and where only your pharmacy’s label can answer.
At a glance
Three rules for a compounded vial
1
Your label beats any guide
Concentration, mixing and beyond-use dates differ by pharmacy. Read your label.
2
Cold, clean, 28 days
Refrigerate, use a new needle and syringe every time, and toss multi-dose vials 28 days after first use.
3
Units are not milligrams
A unit count is only right for one concentration. Confirm yours with the pharmacist.
Why compounded vials need more care than pens
Compounded drugs are not FDA-approved, so FDA does not review their safety, effectiveness or quality before they are sold. Branded pens come in fixed doses. Compounded semaglutide and tirzepatide come in multiple-dose vials or prefilled syringes, in concentrations that differ between pharmacies and sometimes within one pharmacy, and some must be mixed before use. No single storage or mixing rule fits every vial, so we will not invent one.
FDA has stated a few things that apply to all of them. Injectable GLP-1s need refrigeration, and FDA advises against using one that arrives warm or with too little ice. Each needle entry into a multiple-dose vial risks contamination, so FDA recommends a new sterile needle and syringe for every dose and discarding the vial 28 days after first use, even if medicine remains and even if the compounder says it lasts longer.
Lab note
With a pen, the device measures your dose. With a vial, you do. Make sure you know what one unit holds.
The bigger danger is the dose. FDA has received reports of overdoses from compounded semaglutide, some needing hospital care. Most involved people drawing up far more than prescribed: in one example, a 5-unit dose (0.05 mL on a 1 mL insulin syringe) was taken as 50 units. Others came from prescribers converting milligrams to units wrongly. Reported effects included severe nausea, vomiting, belly pain, fainting, dehydration, pancreatitis and gallstones, and because semaglutide lasts about a week, an overdose can take days to settle.
From FDA
Three numbers FDA has published
28 days
after first use, when FDA recommends discarding a multiple-dose vial, even if your compounder’s label says longer
5 to 20 times
the intended dose that some patients injected by mistake from multiple-dose vials, in FDA’s dosing-error reports
990
adverse event reports linked to compounded semaglutide received by FDA as of May 31, 2026, plus more than 730 for compounded tirzepatide
Sources: FDA, Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (current as of October 2026); FDA alert on dosing errors with compounded semaglutide.
Safe storage and mixing, step by step
- Read the whole label before you open the box. Find four things: the concentration (mg per mL), how to store it, whether it needs mixing, and the beyond-use date. If any is missing, call the pharmacy before using it.
- Check the shipment the day it arrives. It should be cold with intact packaging; if it arrived warm, do not use it. Our page on a GLP-1 left out of the fridge covers the branded pens’ limits; a compounded vial follows its own label.
- Mix only with what the label names, in the amount it names. If your vial needs reconstituting, use only the liquid and volume on the pharmacy’s instructions, and ask a pharmacist to walk you through it the first time. More or less liquid changes the concentration, so every unit then holds a different dose.
- Write your dose in units on the box. Ask the pharmacist to confirm: for this vial, my dose of __ mg equals __ units on this syringe. Use the syringe size the pharmacy supplies; FDA has seen errors with syringes far larger than the dose.
- Keep it clean and cold. Refrigerate as labeled, never freeze unless told to, and use a new sterile needle and syringe for every dose. Mark the date of first use on the vial and discard it 28 days later, or sooner if the label says so.
- Dispose of needles safely. Put used needles and syringes straight into a sharps container and follow your local rules when it is about three-quarters full. Our injection day tips cover the rest of the routine.
From our support desk at GLP-1 SOS
If you wrote to us tonight about your vial, here is what we would say.
We would not tell you how long your vial lasts or how many units to draw. Only your pharmacy knows its concentration and beyond-use date, and a wrong guess here is how people end up in the emergency room. Call them and ask them to confirm your dose in units for this exact vial. If you think you took too much, call your prescriber or Poison Control at 1-800-222-1222 now. For the ordinary days after a correct dose, GLP-1 SOS Daily Gut Relief, 2 capsules with dinner, gives ginger and peppermint for digestive comfort and magnesium to support regular bowel movements; ginger tea is a fine brand-free start.*
We answer real questions from real people every day. Write to us if yours is not here.
*GLP-1 SOS Daily Gut Relief supports regular bowel movements and digestive comfort. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.
Use it or set it aside
Safe to use, or set aside and call the pharmacy
Safe to use, per your label
- Arrived cold, packaging intact
- Within its beyond-use date and under 28 days from first use
- Looks the way the label says it should
Set aside and call
- Arrived warm or with melted ice packs
- Cloudy, particles or a color change the label does not describe
- You are unsure how many units hold your dose
Unsure is a reason to call, never a reason to guess.
When to call your doctor
Call your prescriber or Poison Control (1-800-222-1222) right away if:
- You think you injected more than your prescribed dose
- You are vomiting and cannot keep liquids down, or feel dizzy and are urinating much less
- You have severe belly pain that will not go away, with or without vomiting
- You faint, or feel shaky, sweaty or confused, especially if you also take insulin or a sulfonylurea
- You have swelling of the face or throat, or trouble breathing (call 911)
A suspected overdose is never something to sleep off. Semaglutide lasts about a week, and symptoms can build over days.
From the people behind the Lab
You do not have to figure this out alone.
GLP-1 SOS is the daily companion made for life on a GLP-1. Plain answers like this one, a support team that replies to real questions from real people, and daily formulas like GLP-1 SOS Daily Gut Relief, designed around the side effects that come with the medication. The GLP-1 Lab is our free education arm: no login, no paywall, no hype. Side effects are part of the road. Suffering through them is not.
Questions people also ask
How long does compounded semaglutide last in the fridge after mixing?
Only your pharmacy can say; the beyond-use date on its label applies to that product. FDA’s general advice for multiple-dose vials is to discard them 28 days after first use, even if medicine remains and the label allows longer, because each needle entry risks contamination. Use whichever date comes first, and write the first-use date on the vial.
How many units is 0.25 mg of compounded semaglutide?
It depends entirely on your vial’s concentration, so no general answer is safe. In one FDA report, 0.25 mg equaled 5 units for that product; a prescriber wrote 25 units and the patient got five times the dose. Ask your pharmacist to confirm your dose in units for your exact vial and syringe, and write it on the box.
Can compounded tirzepatide be left out of the fridge?
Follow your pharmacy’s label. FDA says injectable GLP-1s require refrigeration and advises against using one that arrives warm. Branded Zepbound pens and vials have specific room-temperature limits in their label, but those numbers apply only to Zepbound, not to compounded tirzepatide. If your vial sat out, call the pharmacy before you use it, and tell them how long and how warm.
Can I reuse a syringe for my compounded GLP-1 to save money?
No. FDA recommends a new sterile needle and syringe for every dose, because reusing them can contaminate the medicine left in the vial and lead to an infection where you inject. Ask your pharmacy to send enough syringes for every dose in the vial, in the size that matches your dose.
Are compounded GLP-1s more likely to cause side effects?
FDA notes that many problems reported with compounded semaglutide and tirzepatide look like the known effects of the approved drugs, and that some may relate to dosing errors or doses beyond the approved labels. Quality can also vary, because compounded products are not FDA-reviewed. Our page on side effects on compounded GLP-1s goes deeper.
Sources (6)
- FDA’s Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. U.S. Food and Drug Administration, content current as of October 1, 2026.
- FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products. U.S. Food and Drug Administration.
- Compounding and the FDA: Questions and Answers. U.S. Food and Drug Administration.
- Best Way to Get Rid of Used Needles and Other Sharps. U.S. Food and Drug Administration, content current as of August 2023.
- Zepbound (tirzepatide) injection, Prescribing Information. Eli Lilly, revised August 2026.
- Poison Control: get help online or call 1-800-222-1222. National Capital Poison Center.
Reviewed by the GLP-1 SOS editorial team · Education, not medical advice · Talk to your prescriber about your dose and your symptoms.
