Insulin and history

Can anyone tell me the history of the U values of commercially available insulin the USA?

I know I took U80 and U100

I believe my mom used U40

and I have seen pictures of vials of U20

Does any know was U40 a commercially available insulin or did I dream it up? Also what are the other insulins available? I knwo U500 is used by some, are there others?

Also how would describe the difference in U values? I have understood it to mean that a person using U20 would need to take 5 times the volume of U20 in order to match the potency of U100? Is that a correct statement?

Inquiring minds want to know?

thanks for any help.


Originally U40 was about the best you could get. Here is a vial from the 1930s of U40 from Lilly. Purification advancements allowed higher concentrations and U40 and U80 were in widespread use. Eventually U100 could be produced consistently and uniformly and in 1973 U100 became standard. And today you can even get U500. U100 means 100 units in ml and U20 means 20 units in 1 ml, thus 5ml of U2 would contain 100 units.

Today only U40, U100 and U500 are generally available. In the US U40 is typically used for pets and has been almost universally been phased out for human use although it may still be use some places globally.

U-40 was by far the most common up until the 70's. By 1980, U-100 had almost completely replaced U-40, and in 1990 only a few third world countries still commonly used U-40 in humans.

I think Vetsulin is still most commonly U-40.

I don't think I overlapped with U-20.

If you use Google News, you can find newspaper ads for insulin in the 50's/60's/70's.

IIRC your diagnosis date you might have been in the window where U-80 was the new one.
If you have any old glass insulin syringes: red marking on outside means U-40, green means U-80. I don't think I ever saw a U-100 glass syringe but the color coding for that would be orange. Did you start on plastic syringes with U-80? Were they green caps? I definitely remember orange and red but do not remember green myself.

I was dx in 1984, and I do remember hearing about U40 and U80 (or maybe U60), but I never saw those on the pharmacy lists in the US, just U100, so I figured they were used in other countries. At that time "human insulin" was the big thing, and many people were in the process of transitioning from pork or beef insulins. There was a lot of mistrust of the "human" type for the first few years, since it was synthetic yet bioidentical to human insulin.

Personally I think U40 should still be available. It would be highly useful for small children. As it is the only viable option is to get U100 and dilute it, which isn't always easy to do depending on where you live.

I did use a green cap disposiable. Only for a small amount of time however. I also remembr the green and red marks on the glass syringes. However I never used one. I only used disposable. I was dx’d in 19974. I think I changed to U100 in 1974 but I started on U80, yes gettign to U100 was a big deal for me. Goodness knows why it stuck with me like that. LOL

Brian it is then a volume issue? Which is why the glass and steel syringes and needles were so large? More volume means you had to go deeper when injecting?


I don't really know, Ira Hirsh says it is because it is a "single understandable strength" (base 10 presumably). He also says it "reduces errors using different insulin concentrations." I suspect that volume was a consideration. The use of syringes for insulin injection is probably far greater than tuberculin use (the other common syringe) and in order to support tuberculin syringes at 50 units doses and below we would have to have U50 or less. Tuberculin syringes are typically 1 ml and use 100 units, generally too large for insulin. All syringes have moved from the huge gonzo stabbing needles to small 31g needles.

What does the U in U100 represent? I know units of concentration such as 1M are 1 mole (6.022x10^23)of X molecule per liter.

So what unit of measurement is the Unit based off of?

It is based on the Platinum-Iridium rabbit unit of insulin.

OK, I made part of that up. No, I didn't make up the rabbit part, just the Platinum-Iridium part. (Although you will note that many metric units such as the kilogram and meter are indeed based on platinum-iridium standards.) See also Hacker's Dictionary definition of Platinum-Iridium


Here are some details on the rabbit unit of insulin: Bioassay of Insulin

Ok, those details of the rabbit thing are confusing. A unit of insulin was standardized as the amount of insulin required to lower the blood sugar of a 2kg fasting rabbit to the convulsion level of 0.045%. Surprisingly under pressure from PETA no more proper calibration of insulin potency can be done.

The bunnies can relax. 1 unit is now defined as 0.0354 mg.


I also started a discussion a while back about that topic, i think the first few responses i got were helpful, so if you are interested in that: