Diabetes in Pets

The long-lasting Humulin U and Humulin L and their Novo Nordisk equivalents have all disappeared by now, and some feline (and perhaps canine) caregivers are desperately looking for substitutes. Some brands of PZI are also being discontinued, but not all.

About your current saved-up supply of Humulin U or L: Health Canada has investigated some Lilly insulins and found them to be stable up to a year beyond their expiry date[1][2]. See Substitutes for Iletin II NPH.

In cats

The most often recommended substitutes on the Feline Diabetes Message Board[3] are PZI[4], Levemir, and Lantus. All three have typical duration in a cat between 10 and 20 hours (each cat varies). Humulin N and Vetsulin/Caninsulin are too harsh and short-acting for most cats. They both typically last only 8-10 hours, peaking sharply after 4 hours, and leaving the cat hyperglycemic for another few hours afterward. Please click on their names for lots of details on usage, action, and where and how to get these longer-acting insulins.

  • PZI Insulins are recommended by many vets for cats (they give good 8-12 hour duration in cats). Dr. Hodgkins prefers PZI Insulins for her protocol
    • Beef PZI is the most like feline insulin, but can usually be obtained only through a vet, and typically has the shortest duration of the three. See PZI Case studies.
    • Beef/Pork PZIVet, formerly known as Blue Ridge, is also recommended and has similar properties[5]. See PZI Vet case studies.

  • Lantus (aka glargine) is tested on felines and gave excellent results in a few well-known studies[6]. Dr. Rand at Queensland university recommends it and publishes a protocol for its use. On the downside, it is expensive since many caretakers report that either the Lantus stops working before the vial is used up or there are "floaties" in the Lantus and the remaining insulin must be discarded. Also, some caretakers, and this Novo Nordisk study[7](full study at this Novo Nordisk site link)[8], have reported that Lantus gives inconsistent results day-to-day. See Lantus case studies.

  • Levemir (aka detemir) is very new and has been used in only a few cases but is showing remarkable results in those few cases, even in cats that were hard to regulate on PZI and Lantus. It is getting a reputation for day-to-day repeatability and reliability. In Germany, several cats have found Levemir to be usable with Dr. Rand's Lantus protocol and with other Lantus protocols. See Levemir case studies. On the other hand, it's not known in the veterinary world, not officially tested on cats, and some people find the very slow onset difficult to adjust to.

Note: The other insulins mentioned below for dogs are not as long-lasting in cats.

In dogs

While Humulin L/Monotard[9], were used quite a bit in treating canine diabetes, Humulin U/Ultratard were very rarely successful--they tend to be unreliable in dogs. Former canine users of either one are advised to try[10] :

  • Caninsulin also known as Vetsulin is advertised to give a good 14-24 hour duration in dogs, with a gentle curve similar to the Humulin L curve.
    • The differences between Humulin L/Monotard and Caninsulin/Vetsulin are in species and strength. Humulin L was a U100 r-DNA/GE/GM insulin; Caninsulin, or Vetsulin in the US, is a U40 porcine insulin. Both are Zinc-suspended and belong to the Lente insulin family. In a Veterinary Information Network online seminar held last November (2005), Dr. Greco indicated her choice of new insulin for a dog who had previously done well on Humulin U would be Vetsulin/Caninsulin, as it is 70% Ultralente insulin[11].

See also Substitutes for Iletin II NPH.

Further Reading



Note: since the only difference between Caninsulin and Vetsulin is the brand name it is sold under, this guide would also apply as an assist for those outside of the US.


It should be noted that Caninsulin is considered an approved treatment for feline diabetes in the UK, Germany, France, Italy and other countries. While it is available in Canada as Caninsulin, and in the US as Vetsulin, the insulin has received approval in both countries for dogs currently. Use of it for treating cats would be considered legal Off label usage.