Understanding mg, mcg & ml
- mg — milligram
- A measure of mass.
- mcg or µg — microgram
- A smaller measure of mass: 1 mg = 1,000 mcg.
- ml or mL — millilitre
- A measure of volume: 1 litre = 1,000 ml.
- mg/ml — concentration
- The mass of a substance in each millilitre of solution.
You can convert mg to mcg directly. Converting mass to volume requires the exact concentration; mg and ml are not interchangeable. These definitions explain labels and do not determine an individual dose.
↑ All topicsCommon measurement mistakes
- Confusing mg, mcg and ml.
- Assuming the same volume has the same amount of medicine in every product.
- Copying syringe markings from a different concentration.
- Misreading a decimal point or the spacing between scale marks.
- Using instructions for a different vial, cartridge or pen.
Confirm unclear measurements with the dispensing pharmacist before use. FDA has reported serious dosing errors with compounded semaglutide when concentrations and measurement units were misunderstood. FDA source
↑ All topicsSimple mass conversions
| Milligrams (mg) | Micrograms (mcg) |
|---|---|
| 1 mg | 1,000 mcg |
| 0.5 mg | 500 mcg |
| 0.1 mg | 100 mcg |
These are unit conversions, not suggested amounts of any medicine. Multiply mg by 1,000 to obtain mcg; divide mcg by 1,000 to obtain mg. Millilitres measure volume and cannot be substituted for either mass unit. [2]
Sources and further reading
- NHGRI: peptide definition
- NIST: metric prefixes
- CDC: injection safety
- FDA: measurement-related errors with compounded semaglutide
The exact product label and device instructions are needed for preparation, storage and use.