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Compounded GLP‑1: units and milligrams.

By Max HP · Updated

Compounded GLP‑1 products are not approved by the FDA, and their labels can sometimes express a dose in units rather than milligrams. That difference has caused real dosing errors. Keeping the two units separate in a log is a small, practical safeguard.

What compounded means

A compounded drug is made by a pharmacy or an outsourcing facility rather than by the manufacturer of an approved product. Compounding has legitimate uses, but it is a different regulatory category. The FDA puts the limit plainly: “the agency does not review compounded drugs for safety, effectiveness or quality before they are marketed.” That sentence is the starting point for every other question about a compounded GLP‑1.

The FDA’s 2026 policy update describes the conditions under which compounded drugs can qualify for the exemptions in sections 503A and 503B of the Food, Drug, and Cosmetic Act. One condition is that the compounded product is not essentially a copy of a commercially available drug. The update notes that tirzepatide and semaglutide do not currently appear on the 503B bulks list or on the drug shortage list. Those are regulatory facts, not a judgment about any one prescription.

If your prescriber has chosen a compounded product, the pharmacy’s label and instructions are the documents that describe what is in the vial. Read them before the first dose, and keep them with the supply.

Compounding pharmacies are licensed by states, and outsourcing facilities are registered with the FDA under section 503B. The two pathways have different rules, and the label may not make the distinction obvious. If you want to know which one made your product, ask the pharmacy. The answer affects the inspection and reporting requirements that apply.

The FDA encourages patients and clinicians to report adverse events and medication errors through MedWatch. That is not a step anyone wants to need, but it is how a pattern becomes visible. A record with the concentration, the dose in both units, the time and the symptoms is the raw material for a useful report. It is also the record your prescriber needs to understand what changed, and it takes only a minute to write down at the time, before the details fade into a general, unreliable memory of the day. That is the whole habit: one entry, one time, one clear unit.

Why units and milligrams get confused

An FDA-approved injectable semaglutide product comes in a pre-filled pen with a standard concentration. The dose is written in milligrams. A compounded vial is different: the concentration is set by the compounder, the volume is drawn with a syringe, and the instructions may express the dose in units. A unit is a volume on that syringe, and its meaning depends on the concentration in the vial.

The FDA describes the failure mode: “FDA-approved injectable semaglutide products are dosed in milligrams, have standard concentrations and are currently only available in pre-filled pens.” It also reports that “patients administered five to 20 times more than the intended dose of semaglutide” in some dosing errors, often after drawing up more than the prescribed volume from a multiple-dose vial. In one example, a patient directed to take 5 units mistakenly took 50 units.

The arithmetic is not the problem. The problem is that the same number can mean different amounts in different vials. A log that stores “10” without saying whether it is 10 units or 10 milligrams has lost the distinction that matters most.

How to keep the units straight

  • Record the concentrationThe amount of drug per milliliter, exactly as the pharmacy label writes it. Without it, a unit entry cannot be interpreted.
  • Record the units and the milligramsIf the pharmacy gives both, store both. If it gives only one, store that and note which one it is.
  • Record the vial size and the beyond-use dateThe date the vial must be discarded, not just the date it was opened. The FDA recommends discarding a multiple-dose vial within 28 days of first use unless the product’s instructions say otherwise.
  • Record the syringeThe size and the markings, especially if the prescribed volume is small. A syringe that is much larger than the dose is easier to misread.
  • Keep the conversion in writingIf the label says units and you think in milligrams, ask the pharmacy for the conversion in writing. A log is not the place to guess.
  • Keep the pharmacy labelA photo is enough. It has the concentration, the dose and the pharmacy’s instructions in one place.

Max HP keeps milligrams and units in separate fields and does not convert one to the other. If you enter a dose in units, the app stores units. If you enter milligrams, it stores milligrams. The two are shown side by side, not merged into a single number.

Questions to ask the pharmacy

The first question is what the concentration is, in milligrams per milliliter, and where it is printed on the label. The second is what the prescribed dose is in milligrams and in units, and which syringe size the pharmacy supplied. The third is the beyond-use date and the storage instructions for this vial, which may differ from the approved product’s label.

The fourth is what to do if a dose looks wrong. The FDA encourages patients to talk with their prescriber or compounder about how to measure and administer the intended dose. That conversation is more useful before the first dose than after a mistake.

If something goes wrong, the FDA’s MedWatch program accepts reports of adverse events and medication errors. A record with the concentration, the units, the milligrams and the time is the kind of detail a report needs. The same record helps your prescriber understand what happened.

Questions

Are compounded GLP‑1 products FDA-approved?
No. The FDA does not review compounded drugs for safety, effectiveness or quality before they are marketed. Compounding is a separate regulatory category with its own conditions. Your prescriber and pharmacy are the source for what is in your vial.
Why is my dose written in units instead of milligrams?
Compounded products can be supplied in vials with different concentrations, and the instructions may express the dose as a volume on a syringe. A unit is not a fixed amount of drug; it depends on the concentration. Ask the pharmacy for both values.
Can I use the same units as an FDA-approved pen?
No. The approved pens have standard concentrations and are dosed in milligrams. A compounded vial may have a different concentration, so the same unit number can deliver a different amount. Ask the pharmacy for the conversion in writing.
What if the vial arrives warm?
The FDA says: “The agency recommends patients not use any injectable GLP‑1 drug that arrives warm or with insufficient refrigeration, as this can affect the drug’s quality.” Contact the pharmacy, note the delivery, and ask for instructions. A box that feels cool is not proof that the cold chain was fine.

Sources

  1. US Food and Drug Administration, “FDA’s Concerns with Unapproved GLP‑1 Drugs Used for Weight Loss.” Content current as of 1 October 2026. Read 3 November 2026.
  2. US Food and Drug Administration, “FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products.” Content current as of 26 July 2024. Read 3 November 2026.
  3. US Food and Drug Administration, “FDA clarifies policies for compounders as national GLP‑1 supply begins to stabilize.” Content current as of 1 April 2026. Read 3 November 2026.
  4. US Food and Drug Administration, “MedWatch: The FDA Safety Information and Adverse Event Reporting Program.” Content current as of 2 November 2026. Read 4 November 2026.
  5. Wegovy® (semaglutide) prescribing information⁠, DailyMed. Revised June 2026. Read 3 November 2026.

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