mg/mL: How to Read a Drug Strength Label
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[Glossary · Mixing and measuring]

mg/mL (milligrams per milliliter)

Also called mg per mL, mg/ml, milligrams per milliliter, drug strength · Reviewed

Definition: mg/mL (milligrams per milliliter) is a strength: how many milligrams of drug are in each milliliter of liquid. It is not the amount in the whole vial or pen. Labels write strength in a few different ways, including mg/mL, mg per total volume and percent, and each one can be turned into mg/mL.

Three ways labels write it

  • Per mL: the Omnitrope 5.8 mg vial is 5 mg/mL after mixing.
  • Per total volume: Wegovy syringes are written as, for example, 2.4 mg/0.75 mL. That is the amount in the whole syringe, not per mL.
  • Percent: the bacteriostatic water label writes 0.9% benzyl alcohol as 9 mg/mL. A percent strength times 10 gives mg/mL.

For how a mixed vial gets its strength, see concentration.

Worked example: per total volume to mg/mL

Wegovy single-dose syringe strengths, divided out to mg/mL
Label strengthMathmg/mL
0.25 mg/0.5 mL0.25 ÷ 0.50.5
1 mg/0.5 mL1 ÷ 0.52
2.4 mg/0.75 mL2.4 ÷ 0.753.2

Cross-check against the label

  1. The Wegovy label says a 3 mL single-patient-use pen holds 9.6 mg.
  2. 9.6 mg ÷ 3 mL = 3.2 mg/mL, and the label prints 3.2 mg/mL next to it.
  3. That matches 2.4 ÷ 0.75 = 3.2 mg/mL from the table.

Common mix-ups

  • Reading mg/mL as mg per vial. A 5 mg/mL vial holding 2 mL has 10 mg in it.
  • Mixing up mg and mL. FDA has linked confusion between milliliters, milligrams and units to dosing errors with compounded semaglutide.
  • Assuming two vials match. FDA notes that compounded semaglutide comes in different concentrations. Dose Track stores the strength with each vial.

Read more on Dose Track: Peptide reconstitution calculator · GLP-1 units to mg charts · Vials and inventory in Dose Track

General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
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Frequently asked questions

Is mg/mL the same as mg?+
No. mg is an amount of drug. mg/mL is how much drug is in each mL. Multiply mg/mL by the volume to get the amount.
What is 0.9% in mg/mL?+
9 mg/mL. A percent strength means grams per 100 mL, so multiply the percent by 10 to get mg/mL.
How do I turn "2.4 mg/0.75 mL" into mg/mL?+
Divide the mg by the mL. 2.4 divided by 0.75 is 3.2 mg/mL.

Sources

  1. Wegovy (semaglutide) US prescribing information, DailyMed
  2. Omnitrope (somatropin) US prescribing information, DailyMed
  3. Bacteriostatic Water for Injection, USP (Hospira) label, DailyMed
  4. FDA: Dosing errors associated with compounded injectable semaglutide products (2024)

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