My 13 year old tomcat was recently diagnosed with diabetes, with a blood glucose level of 30 (very high).

The vet started him on 1.5 units of Insulin (U-40 syringe) a day. After a week his glucose level remained - even increased to 31. The vet put him on 2 units twice daily. A week later, his BG was up to 32. It was getting worse!! So now he is on 3 units twice daily.

I give him a shot at 7 in the morning with a sachet of food. He has access to dry food all day while we are out at work. He's always hungry when my partner gets home at 4, and gives him a pouch then. I then give him another shot at 7pm with a half pouch of food. Then he gets hungry around 10.30 and we give him another pouch.

The vet probably doesn't know that this is his feeding cycle - should I be altering the timing of his shots in accord with this?

  • 3
    What food is he on? You do need to portion his food, he should eat half his daily requirements BEFORE the first shot and other half BEFORE his final shot. When was the last time he had a glucose curve done? Commented Aug 27, 2017 at 12:45
  • 1
    The vet recommended sticking to his usual food, but this was after we'd tried him on an expensive high protein wet food, so it's a mixture of both. He hasn't had a glucose curve done.
    – TCassa
    Commented Aug 27, 2017 at 14:30
  • 4
    Do you have a glucometer at home? Has anyone shown you how to use it? Commented Aug 27, 2017 at 14:34
  • 1
    We do not have a glucometer - currently taking the cat to the vet every week to get it checked as he was only diagnosed a couple of weeks ago.
    – TCassa
    Commented Aug 29, 2017 at 7:57
  • 1
    Thanks for sharing this, my 13 year old tom has also just started 1.5 insulin and has a voracious appetite. Ive been feeding him 4 to 5 times a day and unable to get blood glucose below mid 20s. but now i see that the over feeding is the problem. I will be strict with his meals from now on :)
    – Cheery
    Commented Jul 7, 2022 at 6:54

2 Answers 2


An update after a year

We got very strict with his feeding times, only 2 full meals a day with only the occasional small dry food snacks periodically.

We also only fed him food which had a high meat content or was totally grain free - such as:

Hi-Life - It's Only Natural (The Tuna One)

James Wellbeloved - Senior Turkey

Encore Cat Food

It's all much more expensive than ordinary cat food like Whiskas and Felix, but the results have been very satisfying. I also bought the cat some cat grass, which he enjoys eating after meal times, although I cannot be certain this has been a contribution.

Basically, his blood sugar ranges gradually fell, from around 28mmol-12mmol last year, to between 7mmol and 11mol - results so incredible that he no longer requires insulin at all. I check his blood sugar every two weeks or so to make sure, but he is always well within an acceptable range.

  • 2
    Hey, thanks for coming back to post an update :) Glad to hear he's doing well!
    – Henders
    Commented Oct 16, 2018 at 10:49

You do need to change your feeding practices. From your description, it sounds as though your cat is being overfed, which will just make the diabetes worse.


First – I would change the diet to one appropriate for a diabetic patient, and will help with weight loss. It needs to be low in carbohydrates. There are many veterinary diets out there that would be appropriate, talk to your vet exactly which product to use. It's not something that can be half-done. Of course if the cat does not like the diet, then it needs to be changed to another one formulated for diabetic patients. Trust me that feeding the right food, in the right amounts, is much less costly and stressful than pushing the cat into a diabetic crisis. Getting on the right diet may also allow you to decrease the insulin dose over time.

Purina DM is the most popular diet for diabetic cats in my experience, many clients also like Hill's m/d.


Glucose monitoring is a must in diabetic patients. If you can do this at home it is ideal, using a glucometer by a needle prick in an ear vein (ask your vet for further instructions). A one time glucose reading at the vet is of little use to anyone; the cat is likely already has a stress hyperglycemia at that point so you have no idea if the diabetes is well managed or not. Blood glucose curves are needed for this purpose, whether done by you at home or on an outpatient basis at the vet clinic. Your vet may also recommend fructosamine testing, which gives a better idea of how glucose has been managed over a two week period.


Now getting to the question. You need to alter your feeding cycle. For one thing, I suspect your cat is getting far too many calories being fed wet food four times daily and free choice dry food.

Transition gradually to set meals during the day, no free choice food if possible. This may be a challenge for a cat that has always been a grazer, and your cat may not be happy about it, but you need to control what your cat is eating. Leaving food out all day will not prevent him from becoming hypoglycemic; if it happens he wouldn't think "I need to eat sugar" like a human diabetic might think. He just wouldn't feel good, and would not eat. When his glucose is normal he's just going to keep eating all day whenever he feels like it.

Ask your vet to calculate the caloric needs of your cat based on the diet fed, to make sure you are feeding an appropriate amount.

Different vets will give different recommendations as to when to give the insulin. As cats can be finicky when they want to eat, I always recommend they eat a substantial amount of their meal before any insulin is given. My recommendation is to give the insulin while the cat is eating or within 30 minutes of finishing the meal. I would be cautious giving it before a meal as you cannot be sure how much the cat will eat.

On lower doses of insulin it is less of a concern that a cat will become hypoglycemic, but when giving 3 units twice daily more thought does have to be given with timing of feeding and insulin dosing.

The insulin product you are using may make a difference as to ideal meal timing. Long-acting insulin, glargine (Lantus), is marketed as a "peakless" insulin, implying that it doesn't have to be given with food, but it does still peak in cats who can become hypoglycemic if not eating appropriately.

As these diabetic cats usually need to be on a weight loss diet, I recommend sticking to twice daily feeding regimen, with insulin given at those two mealtimes. A small third or fourth meal is ok as long as you spread out the calories throughout the day, and give most of the food at the time of insulin dosing.

Any changes in diet should not be done suddenly; i.e. don't go from free-feeding to twice daily meals overnight. Just gradually decrease the amount free-fed, and increase the amount fed at set meal times.

If the cat won't eat it's meal, do not give any insulin to be on the safe side. If it's eaten recently (say in the last 6 hours) then you are probably safe to give a half dose of insulin. If the appetite isn't back to normal within the next few hours then your cat may be sick and need to see a veterinarian as soon as possible.

These recommendations are largely based on clinical experience as well as the ISFM Consensus Guidelines on the Practical Management of Diabetes Mellitus in Cats (2015).

Management of diabetic cats can be one of the most challenging things for vets and owners – best of luck in getting your cat well regulated.

  • Many thanks for your detailed response - He is now on two set meals a day and has been for just over a week. He does still get hungry in the meantime so we do feed him a small meal in between when he asks or it - usually James Wellbeloved Grain Free biscuits, which I have seen are recommended for diabetic cats.
    – TCassa
    Commented Sep 5, 2017 at 8:05

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.