Diabetes in Pets
Humulin Zn
Ultralente by Eli Lilly
long-acting r-DNA/GE/GM
U100 Zinc
Line Humulin
Also known as Humulin U
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

This was the Euro brand name Eli Lilly gave its U100, long-acting, Ultralente insulin[1][2]; it was called Humulin U[3] for North America.

Novo Nordisk also made Ultralente insulin under the brand names Novolin U and Ultratard[4][5].

All were crystalline-suspended insulins[6].

What Ultralente Is Not

No Lente-type insulin regardless of species can contain any NPH/isophane insulin[7] or any R/Neutral insulin[8][9].

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[10].

The zinc suspension of Lente-type insulin binds R/Neutral, causing the short-acting insulin to slow, losing its short-acting effect[11][12].

Combining Lente Family Insulins

Insulin manufacturers[13] 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[14][15][16][17].

None of the Lente family of insulins (semilente, Lente, Ultralente) can be combined with[18] 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[19].

Keeping the phenol preservatives in mind, all protamine-suspended insulin mixes would be "off limits" regarding same syringe mixing with any Lente-type insulins[20].

The Novo insulins, Ultratard and Monotard, 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.

Further Reading



  1. Humulin Zn Discontinued July 2004
  2. Lilly EU/UK Product Sheet & Time Activity Profiles
  3. Humulin U, etc.-Ultralente Human Insulin Remedyfind.com
  4. Prescribing Novo Insulins
  5. Ultratard Discontinuation Notice July 2005
  6. EMEA Scientific Discussion-Ultratard
  7. Combining Lente-type Insulins with Phenol-Preserved Insulins
  8. Lente Zinc Suspension Causes Loss Of R/Neutral Short-Acting Effect
  9. Availability of Soluble (R/Neutral) Insulin in Mixed Preparations of Crystalline (Lente) & Ultralente GE Insulins-Clinical Therapeutics-1991
  10. Lente-Type Insulins & NPH/Isophane Insulins-A Bad Combination
  11. 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
  12. Resource Guide 2005-American Diabetes Association
  13. Insulin Producers vs Doctors Re:Combining R/Neutral & Lente-type Insulins
  14. Availability of Soluble (R/Neutral) Insulin in Mixed Preparations of Crystalline (Lente) & Ultralente GE Insulins-Clinical Therapeutics-1991
  15. Absorption Kinetics & Action Profiles-Single Subcutaneous Administration of Human Soluble (R/Neutral) & Lente Insulin-Diabetes Care-1987
  16. Delayed Onset of Action of Soluble (R/Neutral) Insulin After Premixing With Lente Insulin Diabetes Research & Clinical Practice-1983
  17. RxEd.org-Insulin Therapy-Mixing Precautions
  18. Phenol Preservatives & Lente-type Insulins--A Bad Combination
  19. RxEd.org-Insulin Therapy-Mixing Precautions
  20. RxEd.org-Insulin Therapy-Mixing Precautions