Why is insulin dosing measured in “units”? Most other drugs are measured in grams, milligrams, micrograms etc.

Question

It seems strange to have the measuring unit for something be a “unit” instead of a measurement of mass. There is an agreed upon standard for what a milligram or a microgram is. Outside of the context of insulin, a “unit” is undefined and variable. Context: I’m an RN with type 1 diabetes. I understand drug concentrations and insulin dosing. This one just seems like a strange anomaly in the world of measuring medications. My only guess is that the actual hormone is so minuscule to measure that even nanograms and picograms can’t do it?

In: 264

Answer 1

Here is answer I was able to find:

>Historically when insulin was discovered at the turn of the 20th century by Banting and Best, they did not have the advanced technological luxury we have today to readily measure the weight of an insulin molecule. Furthermore, insulin was available in various strengths and concentrations so it was difficult to measure the mass or volume of insulin.

> Scientists in the past however were smart people and they came up with creative ways to do things. Therefore, an indirect model was used to quantify a standard amount of insulin. Like most historical scientific studies, we used animals to test a hypothesis. In the case of insulin, we used rabbits. One international unit of insulin was the amount of insulin required to lower the fasting blood sugar of a rabbit by 2.5 mmol/L. With the advanced technology nowadays, we now know one unit of insulin is equivalent to 0.0347mg of pure crystalline of insulin.

> Now is it easier to dose insulin based on 0.0347mg of insulin or 1 unit?

So it seems that 1 unit was a method of standardization used prior to our ability to more accurately calculate the amount of insulin in a sample. We couldn’t test actual concentration so instead, we standardized around an amount to produce a certain outcome. 1 unit was 1 unit, regardless of concentration, with the delivered volume being the variable.

We likely could change over to a more scientifically accurate system today, but given that most folks who take insulin are not medically minded, it would likely cause more confusion than it is worth. They know to take insulin based on units, so best to just keep that the standard.