Using Insulin to Treat Diabetes Mellitus in Cats

Giving your client’s cat insulin to treat feline diabetes can begin to get difficult as most of the work begins after leaving the practice…

Using Insulin to treat diabetes in felines

Once you have to give them insulin, if you have an owner who is not terribly confident that they are going to be able to pick up a hypoglycaemic event, then I will use Caninsulin (a mix of porcine insulin’s 40iu/ml) because it is shorter acting and does not build up over the 18 – 24 hour period like the Glargine does (and which often results result in a hypoglycaemic event, that can last for hours).

Nevertheless, Marshall and Rand think it is a risk worth taking. The cats usually only end up needing 1 – 4 units of either kind of insulin twice a day – the Glargine especially seems to keep them stable at 2 units twice a day.

Once you push up into the 3 or 4 units, you can bring them into remission, but it is often via a sudden hypoglycaemic event, which is unpleasant all round.  And is, I guess, the reason that the Glargine insulin protocol recommends treating them in hospital.

After giving the cat insulin, the process to stabilise Fluffy at home, usually starts at 1 or 2 units of either kind of insulin twice a day. You need to get the owners to bring the cat in after a couple of days to measure its blood glucose 3 hours after their insulin dose and breakfast.

It does not matter about meal-feeding cats, as they do not get the post-prandial glucose spike (ref: The Cat as Model for Human Obesity and Diabetes; Hoenig) – because they are digesting protein and balancing out the glucose release after it has been deconstructed from protein in the liver.

It is more natural for a cat to graze-feed anyway, so if that is what the cat wants to do, then do not change their feeding habits.

The last thing you want is a cat with an empty stomach while it is getting insulin given to it.  The only reason for feeding them something at the time of giving insulin is, therefore, to make sure they are going to eat.

So Caninsulin given twice a day approximately 12 hours apart – can be 1 hour either way, but reduce the NEXT dose by half if it is more than 2 hours late.  It is OK to skip one dose of insulin a week – so owners can have Saturday night off – because it takes a while for the cat to develop ketosis without the insulin.

The same is true for Glargine, and it is especially important to reduce the next dose if it is closer together than 10 hours.

I haven’t had owners have a cat get a hypoglycaemic event using the Caninsulin, but because the insulin level is going up and down twice a day – rather than the much flatter Glargine control of glucose levels in the blood – you are less likely to get the glycaemic control that allows the pancreas to rest and regain function, and take the cat into remission from the diabetes.

Sometimes you can, especially you can get rid of an initiating event like a renal infection or bad teeth and treatment clears that up, then the cat can come out of the diabetic state.  However, the classic diabetic does not come out of it.

Expert View:
Dosage recommendations by the “Feline Diabetes” Dept.of Queensland University

In some ways I think it is easier to have a cat consistently diabetic, with a stable insulin and feeding regime, than have the problems of going into and out of remission.  Hypoglycaemic episodes are more deadly than just plodding along on enough insulin to prevent ketosis, and some girls (human) use their (uncontrolled) diabetes to lose weight – dangerous but an effective way to regain the weight that the pancreas can service.

So how can you track these cats, especially at home?

I track them by water consumption and weight gain.

Once they start gaining weight (and they will) then they are getting enough insulin.  Then they start drinking (and peeing) less.

You can track an indoor cat’s progress either by weighing the litter tray (if it is a single cat household) to determine it is peeing less, or you can measure the water consumption by using a single jug to top up all the water sources and note the amount used daily.

Otherwise, a cat drinking more, starts as a cat drinking more OFTEN – so the owner notices that it goes to the bowl and then, there it is again, drinking.

After a while, it will sit and drink more at a sitting, but it starts by more frequent drinking of normal amounts.  They rarely sit and drink a whole bowl at one sitting.  It is the same if they have renal issues or diabetes.

Sometimes they start out by wanting water from unusual sources – they seem to like to make the owners turn on the bathroom basin tap for some reason, or drink out of the owner’s cup.  I haven’t really pinned that one down, but it is a common comment from owners in the early stages of increased drinking episodes.

So the owners will notice them drinking less, and I have these cats in each week to weigh them, and test their blood glucose to make sure the insulin is doing SOMETHING!

If, after you gave the  cat insulin, it is going up and the blood glucose is not coming down, then, once you get near 1 unit per kg for Caninsulin, or 0.5 units per kg for Glargine, you are dealing with ‘difficult diabetic’ and you should talk to or refer to a medical specialist.

You are usually then looking for acromegaly or hyperadrenocorticism (or an incompetent insulin injector / poor batch of insulin etc..) and good luck with those.

So if the cats are eating and happy, and no ketones in the urine, but still have a high blood glucose, then increase the Caninsulin by 1 unit twice a day, or the Glargine by 1 unit every second week.  It all depends on the owner and the cat, and it’s sort of done on a wing and a prayer.

I am more worried about hypo’s than by high blood glucose.  Even 1 unit of Caninsulin twice a day is probably enough to keep the glucose metabolism ticking over and provide enough glucose for the cat’s brain and other glucose-dependent organs (kidneys mainly) and prevent ketosis.  You are increasing the protein in their diet so they feed the rest of their body with protein and protein products.

If you want to go at the problem harder, or if the owner can only give cat insulin reliably once a day, then you can use the Glargine insulin – it is the one that the hospital – remission protocol is based on. Again, most cats end up on 1 or 2 units of Glargine twice a day.  The key to using glargine insulin, though, is to make sure the cat NEEDS the second insulin dose.  So I start out having the owner give 1 unit twice a day for a couple of days, to mop up some of the excess glucose in the system, then check the blood glucose level 4 hours after the morning dose.

If it is high, then the second dose is needed, and you may need to increase the amount of glargine to 2 units twice a day.  After a couple more days, the blood glucose needs to be checked just before another dose (ie 12 hours after a dose) to check if the blood glucose is going into the normal zone (10 mmol/L or so), in which case the next dose will push the cat into a hypo.

If the glucose is STILL high (outside the normal range – over 12 mmol/L) then it will need the second dose every day. The Glargine works for 12 – 18 hours, and so rests the pancreas, and that is why it takes the cat into remission.  So the key is to find that ‘tipping point’ where the blood glucose is normal for most of the day as it indicates that the pancreas is starting to work again (I think, I reckon it is rare to get good glycaemic control in an cat without a functional pancreas).

So where does Fructosamine fit in?

You can use Fructosamine to predict whether the cat is going into diabetic remission.  In fact, I will sometimes check the fructosamine levels once the cat’s weight has been stable or rising for a month – if the fructosamine is normal, then the pancreas is working again and the insulin should probably be reduced.

Fructosamine can be thought of as measuring the average blood glucose over the previous two weeks, so it is a slower measure of the glucose level.  It is used, of course, to check whether glycosuria is spurious or due to diabetes.  It’s VERY rare for there to be stress-based glycosuria although lots is written about it.

I also always get a normal blood glucose in a normal cat – the key is to prevent the cat from struggling – the leg movement is what provokes hyperglycaemia, and in extreme (and rare) cases, glycosuria can be due to tubular dysfunction (Fanconi syndrome) – not just ‘stress’.

Stress hyperglycaemia is much over-rated, although the one time I found it was in a cat who was waiting to come into boarding, and was around other cats for a couple of hours before the urine test.  The cat was also intermittently on preds, though it had not had any for a week.

So it happens, but very rarely.  It is, by the way, more immunosuppressive (and obviously hyperglycaemia inducing) for a cat to see another cat, than be given immunosuppressant doses of cortisone.

So, anyway, diabetic stabilisation and management can be a bit of a see-saw and requires significant commitment from the owner, especially in the initial stages.  Which is why I call diabetes a ‘gaol sentence’ – routine and timing is essential, and I warn people that it is better to euthanase a diabetic cat if they think they don’t have time or money to stabilise and maintain it.  I know I would not have time for a diabetic cat, since I already disappoint my ragdoll with my irregular schedule, and it would be terrible to cause a metabolic crisis or suffering through not being able to get the routine right.  Treatment is an option, not a requirement.

The Symogi Overswing

I haven’t heard of the Symogyi overswing being a problem with the glargine.  It is a theoretical problem, and not seen very often in cats.

With a glargine excess, the blood glucose just gets pushed lower and lower.  The hypos are quite severe and quite prolonged.

Much more common are technique problems preventing the blood glucose from stabilising.  The injection technique, storage etc are more likely to prevent response.  Blood glucose curves, in hospital, in cats, are useless.

There are now protocols for owners to test blood glucose at home, and it really is not very hard. A recent protocol even involved getting blood from a footpad stab (rather than the ear vein) and they determined that the cat’s preferred the front feet to be stabbed, and hated the back ones being touched.  They are very sensitive about having their back claws trimmed, so I guess that is the same issue for them.

To get a reliable blood glucose reading is a management problem – the cats have to be seen quickly, and / or kept up high, covered and away from other dogs and  other cats during the waiting time – which is also the reason these 12 and 24 hours glucose curves are going to be useless – that is a whole day of ‘stress’.  Once the stress hyperglycaemia is started, it does not settle down and just ‘flat-lines’ the glucose curve.

What are you looking for with a glucose curve? You are looking for a dip in the blood glucose which indicates the glucose is going into the muscles and brain, and putting weight on, and not going out in the urine and making the cat pee more and drink more.

What is the actual reason diabetic animals lose weight?  It is because they are losing calories out in the urine – that glucose is calories.  And why do they drink more? It is because they pee more.

That glucose in the urine drags water with it, so more urine is produced, so the animal drinks more.  Again, cats are a bit different because they can concentrate their urine so well that they do not need to drink more till quite a way into the problem.  If their kidneys are not fully functional, then they will drink more both because the urine is dilute from reduced kidney function and the glucose osmotic effect.  Cats with renal issues and diabetes together? Are very difficult as the treatments are, in principle, diametrically opposed. High protein vs low protein (or at least low phosphate).  It can be done, but again requires enormous commitment.

Usually cats will stay on the same dose of insulin for a long time once they have been stabilised, or unless another event intervenes.  Most of the cats over the age of 10 that I see with diabetes have an underlying problem – infection, teeth, or cancer or something – and the course of those problems determines the course of the diabetes and its management.  If you have an elderly cat being treated for diabetes, then quite often there is a cancer you are not finding, or the pancreas has effectively worn out, and is filled with amyloid, or there is something else causing a continued decline in the pancreatic output, so their underlying problem is progressing. If there is continued weight loss, or declining renal function, then those cats can be quite hard to stabilise.  Otherwise, if it is a ‘standard’ diabetic, then the dose of and response to insulin tends to be quite consistent.

Juggling a cat with IBD (needing prednisolone especially) and diabetes is possible but fiddly.  Far fewer IBD cats seem to become diabetic, particularly if you can avoid using depo steroids, and can use alternate day preds.  Budesonide is supposedly the answer for the ones who need cortisone for their IBD but become diabetic on ‘systemic’ cortisone, although as I mentioned before, I am not convinced that is the case.  I like to think that if the cortisone has a ‘job’ – as in the dose is not an iatrogenic overdose – then there are relatively few problems with cortisone in cats.  If you can get the diet right for the IBD, then even if it becomes diabetic, you can often juggle diet and metronidazole to keep the cat in diabetic remission, or add in a small daily amount of prednisolone and 3 x weekly Leukeran (chlorambucil) so the insulin requirement does not change.  Needs dedicated and fiscally secure owners though.  I think a pancreatic enzyme supplement is also useful in IBD – may just break the protein down into a less allergenic form before the food gets to the absorptive surface of the GI.

Cyclosprin A can cause diabetes, although not commonly, and is associated with recrudescing toxoplasmosis.  It was very commonly used in renal transplants, although fewer of those are done now than 20 years ago, because managing blood pressure and diet has equalled the longevity gained by transplant.  It is now being considered useful for IBD and atopy in cats, as an alternative to prednisolone, although I still try control the allergens rather than keep hitting the immune system.  Omega-3 fatty acids are also joining the IBD control ‘soup’, to try to reduce the use of pred.

It is VERY important you explain to your nurses the difference between the strengths, doses and the importance of getting the CORRECT syringe for the correct insulin.  The Glargine, at 100 units per mil is 2.5 x stronger (and MUCH longer acting) then Caninsulin, at 40 units per ml.  So going by the units on the syringe, you can hugely over or under dose a cat or whatever if the wrong syringe is used with the wrong insulin. It is easy to kill a cat if you use a Caninsulin SYRINGE to administer a GLARGINE INSULIN dose.  Vet nurses are fabulous, but in general maths is not their strong point, and in a rush, the syringes do look similar so mistakes are easy to make.  Try to make sure it is as infrequent as possible. Fortunately, if the ensuing hypoglycaemia is treated with lots of IV fluids with heaps of glucose in it, then the cats seem no worse for wear after one of these events.

So, how good does control of diabetes need to be to be ‘good enough’?

I think, for most cats, a stable weight and water intake indicates good enough.  There is a lot of extra work put into getting cat’s blood glucose ‘perfect’ – involving regular measurements of the blood glucose and adjusting of the insulin.  I think it is ignoring the general robustness of the organism and its tendency to return to homeostasis.  Maybe regular stabbing of a cat for blood tests is not a welfare issue.  I’d like to see it produce a significantly – evidence-based significantly better – outcome than the lower intensity approach before I could get behind it.  People are going down the road where they think they have to be in total control in order to get a good outcome.  I’m still happy to do a general steering of the metabolism and take credit for the fabulous feedback and recuperative mechanisms that actually get the cat well again.