Canine Diabetes Wiki
Iletin R
R, Neutral by Eli Lilly
U100 none
Action in dogs:
  • onset 10-30 minutes,
  • peak 1-5h,
  • duration 4-10h
Line: Iletin
Also known as: Beef R, beef neutral
Similar to: Hypurin Bovine Neutral
Hypurin Vet Neutral, Betasint Bovine Corriente
Insuvet Neutral
Use and Handling:
Shelf Life: 24 months Type: soluble, clear
When Opened: 28 days room temp.
In Pen: N/A
Notes: Protect from light and heat
Do Not Freeze,
May be used intravenously
See Insuvet Neutral, Hypurin Bovine Neutral or
Betasint Bovine Corriente for current handling information for beef R/neutral insulin.
1975 Lilly JAMA ad

From left-insulins Semilente ("S"), Protamine Zinc ("P"), NPH/isophane ("N"), Regular/neutral/normal ("R"), Lente ("L"), and Ultralente ("U").

Lilly human insulins1992charts

Lilly insulin products-1992. This insulin is shown as Iletin II R.

Note that some countries have the brand name in U40 strength.

North American brand name for Eli Lilly's 100% bovine insulins [1]. This is the "R"/neutral or soluble type; many more types were also produced.

Like all R or neutral insulins, nothing is added (suspensions) to alter the insulin's action or speed. [2] There are no beef/pork mixed R/neutral insulins on the market today--they are all either pure pork or pure beef.

The pure beef Iletin R is equivalent to current insulins Hypurin Bovine Neutral and Betasint Bovine Corriente. [3][4][5]

A short-acting, soluble, non-suspended insulin produced from r-DNA/GE/GM, bovine, or porcine sources. From 1921 to the 1930's when PZI was developed, R was the only kind of insulin available.

While both R/neutral and semilente insulins are considered fast-acting, they differ in a few ways. As above, there's no suspension or buffer [6] in R/neutral; it's totally dissolved and soluble, meaning it can safely be used intravenously. [7]

The very small insulin particles in semilente insulin are suspended by zinc. [6] Semilente is cloudy, has an acetate buffer and cannot be used intravenously.

R/Neutral insulin cannot be reliably mixed with Lente or Ultralente insulins. [8][9] Semilente can; the ratio of 3 parts semilente insulin to 7 parts ultralente insulin produces Lente insulin [6].

R/Neutral Insulins[]


  1. Discontinuation of Lilly Iletin I line of beef/pork insulins. Iletin I R is at left.. Eli Lilly.
  2. Humulin R patient leaflet. Eli Lilly.
  3. Patient Information-Hypurin Bovine Neutral. Net Doctor uk.
  4. Hypurin Bovine Neutral. Wockhardt UK.
  5. Prescribing Bovine Insulin.
  6. 6.0 6.1 6.2 DeRuiter, Jack. Insulin Preparations-Regular Insulin. Auburn University. Cite error: Invalid <ref> tag; name "Auburn" defined multiple times with different content Cite error: Invalid <ref> tag; name "Auburn" defined multiple times with different content
  7. Maddison, Jill E.,Page, Stephen W.,Church, David B. (2008). Small Animal Clinical Pharmacology. Saunders Ltd..
  8. Deckert, T. (1980). Intermediate-Acting Insulin Preparations: NPH (Isophane) & Lente. Diabetes Care.
    Note--in 1980, there were no r-DNA/GE/GM insulins
  9. Resource Guide. American Diabetes Association (2005).
Related pages
Cp wockhardt bovine insulins
89 main
Betasint Bovine Corriente
Hypurin Bovine Neutral
Insuvet Neutral
Hypurin Vet Neutral