Weight-loss injections

In the overwhelming majority of cases the phrase means a GLP-1 receptor agonist — a molecule that mimics an incretin hormone the gut releases after eating, while lasting far longer in the body than the natural hormone does. Semaglutide and tirzepatide are the two names most people mean.

Tirzepatide is not simply a newer semaglutide. It acts at two receptors rather than one, which makes it a different molecule with a different profile rather than an upgraded version of the same thing.

Both are given as a subcutaneous injection, typically weekly, using a pen or a vial-and-syringe depending on whether the product is branded or compounded. Both are prescription-only.

Two other categories get marketed in the same aisle and are worth separating out.

• Lipotropic or "fat-burner" injections — typically B vitamins and amino acids. These are not GLP-1 medicines and are not the thing the research on this category is about.
• Compounded combination products, such as semaglutide combined with vitamin B12. FDA has specifically flagged this pairing as an example of a preparation it may consider essentially a copy of a commercially available drug.
• Peptides marketed for body composition. Separate compounds with separate regulatory status, and several sit in a bulk-substance category FDA has flagged for potential significant safety risks.

None of this means a clinic offering them is dishonest. It does mean that "weight-loss injection" on a price list tells you nothing until you ask what the active ingredient is.

The status of compounded GLP-1 preparations is unsettled and we treat it as under review rather than stating it as settled fact. FDA's guidance to compounders sets out an "essentially a copy" test: a compounded product with the same active ingredient as a commercially available drug, in the same or an easily substitutable strength and by the same route, is generally treated as a copy unless a prescriber documents a significant difference for a specific patient. What that means for any particular preparation is a question for the pharmacy and the prescriber, not something a directory can answer for you.

The practical difference: FDA-approved products have been reviewed for safety, effectiveness and quality before marketing, and compounded preparations have not. FDA has also documented fraudulent compounded semaglutide and tirzepatide carrying false label information, including products naming compounding pharmacies that do not exist, or naming a real licensed pharmacy that did not make them.

Injectable GLP-1 products require refrigeration per their package inserts. FDA has received complaints of compounded product arriving warm or with inadequate ice packs, and advises against using any injectable GLP-1 drug that arrives insufficiently refrigerated.

A licensed clinician reviews your history and current medicines, there is a documented reason this is appropriate for you specifically, the prescription is filled by a named licensed pharmacy, and something is monitored afterwards. A service that cannot describe all four is selling access rather than care.

FDA publishes a list of telehealth warning signs for consumers, and it is worth reading before you hand over a card. Among them: a company claiming a compounded drug is the same as an FDA-approved one, prices that look too good to be true, medicine arriving that looks different from what was pictured, no screening or prescription by a licensed doctor, no licensed doctor reachable after the medicine arrives, and labels with spelling errors, wrong pharmacy addresses, or a pharmacy name that does not check out.

• FDA — FDA’s Concerns with Unapproved GLP-1 Drugs Used for Weight Loss — retrieved 2026-08-06
• FDA — FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize — retrieved 2026-08-06
• FDA — Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks — retrieved 2026-08-06