Peptide safety basics

1. Read the certificate of analysis

A certificate of analysis (COA) covers a single batch, so the first check is that its lot number matches the vial. Under FDA's Q7 guidance for making active drug ingredients, a certificate should list every test with its acceptance limit and a numerical result, carry a date and the signature of the quality unit, and give the original manufacturer's name, address and telephone number.¹¹ A sheet that only says "pass", or gives a purity figure with no limit, date, signature or manufacturer, falls short of that.

What to look for, test by test:

• Identity. EMA's guideline on synthetic peptides names mass spectrometry as a way to measure a peptide's molecular mass and confirm its sequence. The same guideline lists purity, water content, residual solvents, elemental impurities, endotoxins and microbial purity among the tests in a peptide's specification.¹⁴
• Impurities. As a yardstick, the European Pharmacopoeia thresholds that EMA cites for peptide medicines set three thresholds for each peptide-related impurity: reporting above 0.1%, identification above 0.5% and qualification above 1.0%.¹⁴ No regulator standard for research-use products turned up in the sources behind this guide.
• Content. An HPLC purity above 95% can sit alongside a powder that is only 70 to 90% peptide by weight, because counter-ions, such as acetate or trifluoroacetate, and residual water make up the balance.¹⁰
• Endotoxin. FDA has let the Limulus amoebocyte lysate (LAL) test replace the older rabbit pyrogen test for over 30 years, and USP and AAMI standards call for pyrogen and endotoxin testing of both components and finished products.⁶

Lot matching is explained on the lab results page, and What are research peptides? describes the test methods in more depth.

2. Know what tests of online products have found

Independent lab tests explain why the paperwork matters. In a 2024 study, researchers ordered semaglutide from illegal online pharmacies, and all 3 vials that arrived were judged probable substandard and falsified products: endotoxin in every one (2.1645 to 8.9511 EU/mg), 28.56% to 38.69% more drug than labeled, and purity of 7.7% to 14.37% where the labels promised 99%.¹ A 2018 Belgian analysis of the 10 falsified peptide drugs seen most often, sourced from three suspected illegal internet pharmacies, found that the amount of drug per unit varied widely, that cysteine-containing peptides were only 5% to 75% pure, and that one sample held lead while several held arsenic at levels reaching ten times the ICH limit for injectable drugs.²

Health Canada's April 2026 warning says unauthorized peptide products may hold too much or too little of the active ingredient, or none at all, unlisted or unknown ingredients, and contaminants such as solvents, heavy metals, particles of fiber, glass or plastic, bacteria, fungi or endotoxins.¹⁵

3. Handle every vial as sterile

FDA's concern with injectable products is that they enter the body directly, sometimes straight into the bloodstream, skipping some of its main protections against toxins and microbes.³

Opened vials do get contaminated. In a 2013 study at a pulmonary teaching hospital in Iran, 11 of 205 opened single- and multiple-dose vials (5.36%) grew microbes, mostly gram-positive bacteria led by Staphylococcus epidermidis.⁸ In a hospital study in Ethiopia, sampled in 2021 and published in 2023, 21 of 384 opened injectable medicines (5.5%) grew bacteria. All of the contaminated samples were from multiple-dose vials, and contamination was strongly associated with reuse of a syringe or needle.⁹

A preservative is not a guarantee. CDC says the preservative in a multiple-dose vial does nothing against viruses and cannot fully stop bacterial contamination.¹³ CDC's injection safety guidance sets out these practices:¹²¹³

• Disinfect the rubber septum with alcohol before piercing it.
• Enter a vial only with an unused needle and an unused syringe.
• Never leave a needle in the septum between uses.
• Write the opening date on a multiple-dose vial. CDC's limit is 28 days unless its maker sets a different one.

Before use, the bacteriostatic water label says to check that the solution is clear and the seal intact, and to inspect a mixed drug for clarity, particles and discoloration.⁷ The reconstitution guide puts these steps in order, and alcohol swabs are on the supplies page.

4. Store it so it stays what the certificate describes

A certificate describes a batch when it was tested. Bachem notes that powder which takes up moisture from the air ends up with less peptide in each milligram, and that dissolved peptides may slowly break down even in sterile solution.¹⁶ The storage guide gives the temperatures and time limits that peptide makers and approved labels set.

5. Measure carefully

Measuring errors are a safety problem in their own right. FDA has reported people taking 5 to 20 times the intended dose from multiple-dose vials of compounded semaglutide, and said confusion among milliliters, milligrams and syringe units may have contributed.⁵ Dosing basics explains the units, and the reconstitution calculator and peptide calculator show the arithmetic.

6. Know the side effects sources report

Peptides for weight loss: GLP-1 products

• Approved medicines. The side effects on the labels of the approved GLP-1 medicines are collected on the GLP-1 side effects page.
• Compounded versions. Through May 31, 2026, FDA logged 990 adverse event reports for compounded semaglutide and more than 730 for compounded tirzepatide, and it says these events are likely underreported, since state-licensed pharmacies other than outsourcing facilities have no federal duty to report them to FDA.⁴
• Measuring errors. Overdoses after dosing errors with compounded semaglutide brought reports of acute pancreatitis, gallstones, dehydration, fainting, headache and migraine as well as nausea, vomiting and abdominal pain, and some people needed hospital care.⁵
• Research-labeled products. FDA urges consumers to avoid research-labeled GLP-1 products, which it calls of unknown quality and possibly harmful.⁴

Other peptides: FDA's safety reviews

FDA's reviews of substances nominated for pharmacy compounding include these notes on peptides that are also sold for research:¹⁷

• BPC-157: possible immune reactions (immunogenicity), possible impurity and characterization problems, and no or only limited safety information; FDA says it lacks enough information to know whether it would cause harm in humans.
• CJC-1295: serious adverse events, among them a raised heart rate and a systemic vasodilatory reaction, with limited clinical data available.
• Ipamorelin: a published study of intravenous use to improve gastric motility, in which serious adverse events, including death, occurred.
• Melanotan II: case reports in the literature of priapism, melanoma, sympathomimetic toxidrome and posterior reversible encephalopathy syndrome.
• TB-500, MOTS-c and KPV: no human exposure data identified.

Side effects for each compound are covered in its profile, listed in Peptides A to Z.

From the injection and the diluent

• The bacteriostatic water label lists reactions that can come from the solution, the added drug or the mixing or injection technique: fever, tenderness, abscess, tissue death or infection at the site, vein clots or inflammation spreading from the site, and leakage into nearby tissue.⁷
• EMA's standard warning for medicines containing benzyl alcohol, the preservative in bacteriostatic water, is that it may cause allergic reactions.¹⁸ The bacteriostatic water label is also marked not for use in newborns.⁷
• Health Canada warns that unauthorized injectable peptide products may lead to infections and allergic reactions.¹⁵

Anti-doping status

Athletes face a separate risk. Under WADA's 2026 Prohibited List, BPC-157 is banned in and out of competition as a non-approved substance (class S0), and the S2 class names CJC-1295, sermorelin, tesamorelin, AOD-9604 and TB-500 among its examples.¹⁹