Mar Vista Animal Medical Center

3850 Grand View Blvd.
Los Angeles, CA 90066



(original graphic by

Achieving regulation in a diabetic cat can be tricky. In most cats, finding an insulin that lasts long enough is a substantial problem. Glargine insulin (brand names Lantus® and Basaglar® as well as the new bioequivalent Semglee®) is approved only as a human product but its use has become common in diabetic cats and many consider it to be the first choice of insulin for a newly diagnosed diabetic cat. Detemir (Levemir®) insulin is another long-acting insulin for humans which is gaining popularity in veterinary use.

In human diabetes mellitus, the trend has been towards the use of ultra-short acting synthetic insulin (like Humalog®) at meal time and a once a day long-acting peakless insulin (such as glargine insulin) to provide general blood sugar control throughout the day. Glargine insulin is readily available at any drug store and is designed to be long-acting and provide a diabetic person with a "tone" of sugar control that lasts all day. In cats, glargine and detemir are not peakless; they definitely have a high point and low point but they do (in most cats) last long enough to control blood sugar levels throughout the day. In newly diagnosed diabetic cats, studies with glargine show such good control when used in combination with a low carbohydrate diet that many cats revert to a non-diabetic status in a matter of weeks. In one study, six out of seven cats were in remission after only 4 weeks of glargine therapy.

Before getting too excited, it is important to realize that diabetic remission is about good regulation early in the course of the disease rather than having a magic product. Cats that have been diabetic for some time tend not to experience remission and if your cat is well-regulated on another insulin, it is not worth changing and having to re-regulate your cat.

What you need to Know:

  • Even though glargine and detemir are long-acting insulins, it probably will need to be given twice a day just like other insulins. Further, every cat is different and some cats metabolize these insulins so quickly that they are not long-lasting at all and another insulin is a better choice.

  • Glargine insulin cannot be diluted nor can detemir. The feline dose of insulin is generally only a few units of insulin and the gradations on an insulin syringe are tiny. With insulins other than glargine or detemir, dilution is possible so that measuring is easier. The long-activity of glargine depends on the formation of small crystals where it is injected. Diluting glargine interferes with the crystals and the same is true with detemir.

  • Glargine and detemir are available in a 3 ml (300 unit) pen ejectors and in 10ml (1,000 unit) bottles. (Brand name Lantus® is available in either vial or pen as is Semglee® but Basaglar® is only available in the pen format). In order to be cost effective, vials and pens must be refrigerated after they are opened. Glargine insulin has been formally studied and found to retain activity for 6 months if refrigerated.  The 10 ml bottle of glargine will expire in one month if it is not kept refrigerated. Detemir has been studied by its manufacturer and the vial or pen will last 40 days whether it has been refrigerated or not. That said, refrigerated open pens or vials are commonly refrigerated for 3-4 months and appear to maintain strength.

  • As mentioned, glargine and detemir come in dosing pens. These are becoming more popular for two reasons: they are much less costly to buy compared to vials which are larger and they are easier to use as they have a dial-a-dose mechanism. The biggest problem is that the disposable needles, which screw onto the pen for single use, are made for human use and they are short (about 1/4 " in length) and may not penetrate cat skin fully. If the needle does not penetrate the skin, the insulin injection will not properly enter the body.

    If you choose a pen instead of a vial for insulin use, you will likely need to get compatible needles in a longer length. Lantus®, for example, is made by Becton Dickinson. All Becton Dickinson pens are compatible with all Becton-Dickinson needle tips. Be sure to order the half inch needles for your pen rather than the 5/16" that human diabetics use. Check with your pharmacist about exactly what needle tips to get to go with your particular brand of pen.

  • Because of the strong chance of a cat going into remission (i.e. becoming non-diabetic), it is important for the owner to be well informed on recognizing the signs of hypoglycemia and adhering to the doctor's recommendation on when to have glucoses checked.

  • The expense of human insulin has come to be extreme in the U.S. and all of the insulins discussed here are made for human use. It is helpful to know that Basaglar® pens are typically around 2/3 the cost of Lantus® and Semglee® products are typically approximately half the cost of Lantus®.
(original graphic by


The high remission rates reported for diabetic cats apply to cats newly diagnosed with diabetes. Other cats who were switched to glargine  or detemir for better glucose control after having been diabetic for years do not tend to revert to non-diabetic status.

For more details on how to administer insulin to your cat, click here.

Page posted: 5/15/2017
Page last updated: 10/24/2021