Diabetes in Pets
Humulin U
Ultralente by Eli Lilly
long-acting r-DNA/GE/GM
U100 Zinc
Line Humulin
Also known as Humulin Zn
Similar to  
Action in cats  
  • onset Xh
  • peak Xh
  • duration: Xh
Action in dogs  
  • onset 1-8h,
  • peak 4-16h,
  • duration 8-28h
Use and Handling
Type cloudy
Shelf Life 24 months
When opened 28 days
In pen N/A

Humulin U[1] is a long-acting, Ultralente insulin formerly produced by Eli Lilly[2], who stopped producing it in July 2005[3][4][5][6].

Lilly called it Humulin Zn[7][8] in the UK.

Comparable to Novo Nordisk's Ultratard[9][10] and Novolin U. All of them were crystalline-suspended insulins[11].

What Ultralente Is Not

No Lente-type insulin regardless of species can contain any NPH/isophane insulin[12] or any R/Neutral insulin[13][14].

Both are chemically impossible: the phenol preservative present in NPH/isophane alters the action of Lente-type insulins, creating a mixture with an approximate action of R/Neutral[15].

The zinc suspension of Lente-type insulin binds R/Neutral, causing the short-acting insulin to slow, losing its short-acting effect[16][17].

Combining Lente Family Insulins

Insulin manufacturers[18] indicate that R/neutral and semilente, Lente, ultralente insulins are able to be combined in the same syringe, but only just before injection. In pre-filled syringes, the zinc suspension of the Lente-type insulins binds the R/neutral, causing it to lose its short-acting effect. Various studies have documented this, and some doctors advise against using R/neutral in the same syringe with the Lente family of insulins[19][20][21][22].

None of the Lente family of insulins (semilente, Lente, Ultralente) can be combined with[23] NPH/isophane insulins. The phenol preservatives present in NPH-type insulins alters the Lente-types to the point where they become a close approximation of R/neutral, with regard to action[24].

Keeping the phenol preservatives in mind, all protamine-suspended insulin mixes would be "off limits" regarding same syringe mixing with any Lente-type insulins[25].

The Novo insulins, Novolin U and Ultratard, were available slightly longer in Europe.

From the announcement: Monotard and Ultratard will not be available in the UK after February 2006. The discontinuation of these insulins was initially announced in September 2004. Initially the discontinuation was scheduled for February 2006, however this date has now been brought forward to October 2005.

See also Substitutes_for_Humulin_U_and_L

Further Reading



  1. Humulin U carton photo.
  2. Humulin U, etc.-Ultralente Human Insulin Remedyfind.com
  3. Humulin U Patient Leaflet
  4. Humulin U Carton Photo
  5. US-FDA Humulin U Discontinuation Notice
  6. Lilly US-Humulin U/Humulin L Discontinuation Sheet
  7. Lilly EU/UK Product Sheet & Time Activity Profiles
  8. Humulin Zn Discontinuation Notice 2004
  9. Prescribing Novo Insulins
  10. Ultratard Discontinuation Notice July 2005
  11. EMEA Scientific Discussion-Ultratard
  12. Combining Lente-type Insulins with Phenol-Preserved Insulins
  13. Lente Zinc Suspension Causes Loss Of R/Neutral Short-Acting Effect
  14. Availability of Soluble (R/Neutral) Insulin in Mixed Preparations of Crystalline (Lente) & Ultralente GE Insulins-Clinical Therapeutics-1991
  15. Lente-Type Insulins & NPH/Isophane Insulins-A Bad Combination
  16. Intermediate-Acting Insulin Preparations: NPH (Isophane) & Lente Diabetes Care-1980
    Note--in 1980, there was only beef Lente-type insulin--no pork or r-DNA/GE/GMLente insulins
  17. Resource Guide 2005-American Diabetes Association
  18. Insulin Producers vs Doctors Re:Combining R/Neutral & Lente-type Insulins
  19. Availability of Soluble (R/Neutral) Insulin in Mixed Preparations of Crystalline (Lente) & Ultralente GE Insulins-Clinical Therapeutics-1991
  20. Absorption Kinetics & Action Profiles-Single Subcutaneous Administration of Human Soluble (R/Neutral) & Lente Insulin-Diabetes Care-1987
  21. Delayed Onset of Action of Soluble (R/Neutral) Insulin After Premixing With Lente Insulin Diabetes Research & Clinical Practice-1983
  22. RxEd.org-Insulin Therapy-Mixing Precautions
  23. Phenol Preservatives & Lente-type Insulins--A Bad Combination
  24. RxEd.org-Insulin Therapy-Mixing Precautions
  25. RxEd.org-Insulin Therapy-Mixing Precautions