The answer to most problems on this page is the same, and it is deliberately conservative: when in doubt, discard. You cannot test a vial at home for sterility, strength or breakdown products. Anything you do to "rescue" one (heating, filtering, shaking, adding more liquid) makes it less trustworthy, not more.
Mixing problems
The powder will not dissolve
- Do: stand the vial upright at room temperature for 10 to 15 minutes, then swirl gently again. Some powders are slow.
- Do not: shake it, heat it, or add more diluent on a guess. Heat and agitation damage peptides [1][2], and extra diluent changes your concentration.
- Still undissolved after that (grains, flakes or a gel that will not go): discard. Approved labels say not to use a solution with solid particles in it [3].
The liquid is cloudy
- Cloudiness that appears straight after mixing and clears within a few minutes was usually just tiny air bubbles.
- Cloudiness that stays, or that appears later in a vial that used to be clear, means discard. It can be clumped peptide, bacterial growth, or something that was never meant to be in the vial. Labels are unambiguous: do not use a cloudy solution [3][4].
- A solution that turns cloudy or forms crystals in the fridge and clears when warm is still not one to use. Discard.
Foam on top
- Foam means the diluent went in too fast or the vial was shaken.
- Do: leave the vial standing in the fridge. Foam usually settles within minutes to an hour.
- A single episode of foam that settles is not a reason to discard. Foam that persists for hours, or a vial that was shaken hard, is questionable: agitation at the surface between air and liquid is a known cause of peptide clumping [1][2]. If the liquid is anything other than clear afterwards, discard.
Bits of rubber in the vial
- Small grey or dark fragments are pieces of stopper cut out by the needle ("coring").
- Discard the vial. Do not try to draw around them.
- Repeated punctures of the same stopper make it more likely.
The diluent sprayed in, or the plunger was pulled out of your control
- Some vials are sealed under partial vacuum. If the liquid rushed in and foamed, treat it as foam (above).
- If liquid sprayed out, or you lost some diluent, your concentration is no longer what you calculated. If you cannot say exactly how much went in, discard.
Problems when drawing a dose
Air bubbles in the syringe
- Do: hold the syringe needle-up, tap the barrel so bubbles rise, push them back into the vial, then re-draw to your mark [4][5]. If there are many, push everything back and draw again slowly [5].
- A tiny bubble in an injection under the skin is generally considered harmless. The problem with bubbles is that they take the place of liquid, so you get less than you measured.
It is hard to pull liquid out
- Pressure in the vial has dropped. Inject a volume of air equal to your dose before drawing [5]. Do not pump large amounts of air in: too much can force liquid back out through the needle hole [5].
The needle touched something, bent, or was dropped
- Replace the whole syringe. A needle that has touched a finger, the table or the outside of the vial is no longer sterile [6].
You drew the wrong amount
- Before injecting: push it back into the vial and draw again, or discard the syringe and start over with a new one.
- After injecting too much: this is a possible overdose. Do not wait for symptoms. Call a poison centre (US: 1-800-222-1222) or a clinician, with the vial in hand, and see the emergency page.
- After injecting too little: do not "top up" with a second injection unless your product's instructions or a clinician say to. You do not know exactly how much went in the first time.
Problems during or after the injection
- Liquid leaks back out of the skin: next time, push the plunger more slowly and keep the needle in for a slow count of five or longer before withdrawing [4]. Do not re-inject to make up for it.
- Blood in the syringe or at the site: a drop of blood at the site is normal; press with gauze [4]. A bruise may follow.
- It hurt more than usual: if the pain was sharp and deep, the needle may have reached muscle; see needle length in injection basics. Use a different spot next time.
- A lump, redness or itching afterwards: see the "after an injection" list in warning signs.
Storage accidents
| What happened | Conservative answer |
|---|---|
| Mixed vial left out for a short, known time (an hour or two at normal room temperature) | For an approved product, check the label's room-temperature allowance. Otherwise return it to the fridge, and shorten how long you keep it. |
| Mixed vial left out overnight, or for an unknown time | Discard, unless it is an approved product whose label allows it [4][8]. |
| Left in a hot car or in direct sun | Discard. |
| Froze (back of the fridge, ice pack in transit) | Discard. Labels say not to use a peptide product that has been frozen [4][8]. |
| Power cut | If the fridge stayed closed and still feels cold, treat it as a short excursion. If the contents warmed to room temperature for many hours, treat as "left out overnight". |
| No date on the vial | Discard. |
| Dropped vial, no visible crack | Hairline cracks can let bacteria in. If you cannot be sure it is intact, discard. |
See storage for what the labels of approved products allow.
Missed doses
Approved products each have their own rule. Use the rule on your product's label, not a general one. The examples below show how much they differ.
Weekly injections
| Product | Labelled rule for one missed dose |
|---|---|
| Tirzepatide (weekly) | Take it as soon as possible within 4 days (96 hours). After that, skip it and take the next dose on the usual day. Doses must be at least 3 days (72 hours) apart. [7] |
| Semaglutide, weight-management label (weekly) | 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. [8] |
| Semaglutide, diabetes label (weekly) | Take it as soon as possible within 5 days. After that, skip it and take the next dose on the usual day. [9] |
After a longer gap, the rule changes. The semaglutide weight-management label says that if two or more doses in a row are missed, treatment may need to restart at a lower dose and be stepped up again, to limit stomach and gut side effects [8]. Going straight back to a high dose after a break risks severe nausea and vomiting, which is why labels require stepping up again [8][10]. Ask the prescriber.
Daily injections
- Do not double up. The liraglutide label says: if you miss a daily dose, take the next dose as usual the following day, with no extra dose and no increase to make up for it [10].
- After more than 3 days without a dose, the same label says to restart at the lowest dose and step up again [10].
Products with no label
There is no tested rule. A conservative approach, more cautious than the weekly labels above:
- skip the missed dose and carry on with the next one at the normal time;
- never take two doses close together to "catch up";
- after a long break, do not resume at the previous amount without advice from a clinician.
Sources
Checked 13 November 2026.
- Nugrahadi PP, Hinrichs WLJ, Frijlink HW, Schöneich C, Avanti C. "Designing Formulation Strategies for Enhanced Stability of Therapeutic Peptides in Aqueous Solutions: A Review." Pharmaceutics. 2023;15(3):935. https://doi.org/10.3390/pharmaceutics15030935
- Zapadka KL, Becher FJ, Gomes dos Santos AL, Jackson SE. "Factors affecting the physical stability (aggregation) of peptide therapeutics." Interface Focus. 2017;7(6):20170030. https://doi.org/10.1098/rsfs.2017.0030
- Tesamorelin for injection (Egrifta WR), US prescribing information and instructions for use, DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=839334d3-8c1d-4c26-9036-2ab524a6ea75
- Tirzepatide (Zepbound) single-dose vial, Instructions for Use (revised April 2026). (link not shown: non-primary host)
- MedlinePlus Medical Encyclopedia. "Drawing medicine out of a vial." https://medlineplus.gov/ency/patientinstructions/000530.htm
- U.S. Centers for Disease Control and Prevention. "Preventing Unsafe Injection Practices." https://www.cdc.gov/injection-safety/hcp/clinical-safety/index.html
- Tirzepatide injection (Zepbound), US prescribing information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=487cd7e7-434c-4925-99fa-aa80b1cc776b&type=display
- Semaglutide (Wegovy), US prescribing information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=ee06186f-2aa3-4990-a760-757579d8f77b
- Semaglutide (Ozempic), US prescribing information. (link not shown: non-primary host)
- Liraglutide (Saxenda), US prescribing information, DailyMed. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=7b11f6ac-4c27-4748-9e65-22d4cf3adfb4&type=display