What are units when referenced for medications?

[Double-Helix, BSN, RN]

It does depend on the drug.

For insulin, a unit is a unit. That's how insulin is measured. Insulin dosages are calculated based on blood glucose and grams of carbohydrates consumed. Because insulin is a unique medication, the measurement is in units for simplicity. (1 unit of insulin does not equal one mL.) Insulin syringes are labeled in units for accuracy.

There are also International Units, often known by the abbreviation IU. IU is a measure of the biological effect of a medication and mostly used in pharmacology. IU's are primarily seen when talking about vitamins. Keep in mind that most hospitals do not allow drugs to be ordered in IU dosages.

As far as the other medications, there are several different units:

Grams (g), milli-grams (mg), micro-grams (mcg), and milli-liters (mL) are the most common. You might also see dosages based on weight. For example, a pediatric dose might be measure as 1 mg per kg (kilogram) of weight. A vaso-active drug on a continuous drip might be measure in mg per kg of weight per minute. IV fluids are usually ordered in mL's per hour.

A standard drug reference guide will tell you what the usual dosage range is for each separate medication. A good drug guide is a nurse's best friend!

[SHGR, MSN, RN, CNS]

One unit of U-100 insulin (the vast majority of insulin) is 1/100 of an mL. One unit of U-500 insulin is 1/500 of an mL, which is much more concentrated and rarely used.

There are a few other medications that are measured in units (bicillin and heparin come to mind) but there is no one standard "unit" across the board, unlike mg or cc that have a measurement that is standard across the world. A unit of insulin has no relationship whatsoever to a unit of heperin or a unit of bicillin, unlike the standard metric types of dosing. I think you just have to learn them with experience.