Units or milligrams? Why there is no one conversion

By Ümit Can Erim · Published 27 August 2026 · Updated 27 August 2026 · Sources checked 27 August 2026 · How these guides are written

If you have searched for how many units make up a milligram of semaglutide, the honest answer is that nobody can tell you without knowing your vial. A unit is a mark on a syringe (a volume) and how much medicine sits in that volume depends on the concentration of the particular vial in your hand. FDA has documented what happens when that is guessed: patients administering five to twenty times the dose they meant to.

Read this first. This page quotes a public FDA alert. It does not convert anything for you, and it does not tell you what your dose is or should be: that number belongs to the person who prescribed it and to the label on your own vial. If you think you have taken more than intended, contact your prescriber or seek medical care.

What FDA reported

On 26 July 2024 FDA published an alert about compounded injectable semaglutide. Its opening sentence is the whole problem in one line: "FDA has received reports of adverse events, some requiring hospitalization, that may be related to overdoses due to dosing errors associated with compounded semaglutide injectable products."

The alert is specific about how. "The majority of the reports described patients mistakenly drawing up more than the prescribed dose from a multiple-dose vial during self-administration. In these instances, patients administered five to 20 times more than the intended dose of semaglutide." And the example it draws a figure for: patients told to give 5 units (0.05 millilitre) from a vial using a U-100 insulin syringe "mistakenly administered 50 units instead."

Prescribers made the same class of error in the other direction. "One provider intended to dose 0.25 milligrams (5 units), but prescribed 25 units instead, leading to a patient receiving five times the intended dose and experiencing severe vomiting." Another "prescribed 20 units instead of 2 units, affecting three patients."

A unit is not an amount of medicine

This is the part that makes the error so easy to make. Insulin syringes are marked in units because insulin has a standard concentration, so on those syringes a unit reliably means a known amount. Semaglutide has no such convention. FDA puts it plainly: the instructions "may instruct users to administer semaglutide injections in 'units' (the volume of which may vary depending on the concentration), rather than milligrams or milliliters."

So "25 units" is not a dose. It is a distance on a barrel. Two vials of different strength, the same 25 marks, two different amounts of drug.

Why the concentration is not something you can look up

Because it is not standard. FDA: "Product concentrations also may vary depending on the compounder, and a single compounder may offer multiple concentrations of compounded semaglutide products." Not merely different between suppliers: different within one supplier. A conversion table you find online was written against somebody else's vial, and the alert describes a patient who searched online for exactly this and took five times the intended dose as a result.

The approved products avoid the whole question by construction. FDA notes they "are dosed in milligrams, have standard concentrations and are currently only available in pre-filled pens." There is no syringe to read, so there is no reading to get wrong.

Two things the alert adds in its footnotes

Both are easy to miss and worth knowing. First, some compounded products contain more than semaglutide (FDA names cyanocobalamin (B-12), pyridoxine (B-6), levocarnitine and NAD) and says "the safety and effectiveness of combining semaglutide with other ingredients has not been established." Second, some use salt forms: "semaglutide sodium and semaglutide acetate. The salt forms are different active ingredients than is used in the approved drugs."

What the alert asks people to do

Its advice to patients is one sentence and it is not a calculation: "FDA encourages patients to talk with their health care provider or compounder about how to measure and administer the intended dose of compounded semaglutide." To prescribers and compounders it asks for the right syringe size for the intended dose, and for counselling on how to measure it.

It also asks for reports. Adverse events and medication errors go to MedWatch, FDA's adverse event reporting programme.

What a log can do here, and what it must refuse to do

A record helps with the part that is factual: what was in the vial, what the prescriber said the dose was, what you gave and when. That is worth having in one place, and it is what you are asked for if something goes wrong.

What it must not do is convert. Dozify will not turn "25 units" into a number of milligrams, and if you import a history from another app whose dose column is written in units, those rows are refused and shown to you rather than silently converted, because the conversion needs the concentration of that particular vial, and a file does not carry it. Guessing it is the error this whole page is about.

Record what was decided, not what was guessed

Doses, vials and dates in one place, on your phone. Dozify records what you and your prescriber decided; it never proposes a dose and never converts a unit it cannot verify.

Download the app See how vial tracking works →

Questions

So how many units is 0.25 mg?

There is no answer that is true of every vial, which is exactly why the errors happened. It depends on the concentration of yours. The figure FDA reproduces uses 5 units for 0.25 mg for one particular product, and the same alert stresses that concentrations vary between compounders and within one compounder. Ask the person who prescribed it or the pharmacy that made it.

Is compounded semaglutide FDA-approved?

No. FDA: "compounded drugs do not undergo FDA premarket review for safety, quality or effectiveness" and "should only be used for patients whose medical needs cannot be met by an available FDA-approved drug."

I think I injected too much. What did FDA see happen?

Seek medical care first. For context, the reported events were "gastrointestinal effects (e.g., nausea, vomiting, abdominal pain), fainting, headache, migraine, dehydration, acute pancreatitis and gallstones." The alert also notes that "a prolonged period of observation and treatment for overdose symptoms may be necessary due to the long half-life of semaglutide of about one week."

Why did my import get refused when the dose column said units?

Because writing 25 units into a milligram field would record fifty times the dose in some vials, and nothing downstream would question it. Those rows are listed for you with the reason instead, so you can enter them with the amount your prescriber uses.

Educational information, not medical advice. Dozify is a personal tracking app, not a medical device. This page quotes a public FDA alert and does not recommend a dose, a conversion, a schedule or a course of action for any individual. Always follow the instructions that came with your medication and your prescriber's directions. If you have severe symptoms, seek medical care or call your local emergency number.