Diabetes in Pets

Blood sugar guidelines[]

  • Absolute numbers vary between pets, and with meter calibrations. The numbers below are as shown on a typical home glucometer while hometesting blood glucose, not necessarily the more accurate numbers a vet would see (though many vets use meters similar to those used in hometesting). For general guidelines only, the levels to watch are approximately:
mmol/L mg/dL(US)
<2.2 <40 Readings below this level are usually considered hypoglycemic when giving insulin, even if you see no symptoms of it. Treat immediately[1]
2.7-7.5 50-130 Non-diabetic range[2] (usually unsafe to aim for when on insulin, unless your control is very good). These numbers, when not giving insulin, are very good news.
3.2-4.4 57-79 This is an average non-diabetic cat's level[3][4], but leaves little margin of safety for a diabetic on insulin. Don't aim for this range, but don't panic if you see it, either. If the number is not falling, it's healthy.
5 90 A commonly cited minimum safe value for the lowest target blood sugar of the day when insulin-controlled.
7.8 140 According to the American Association of Clinical Endocrinologists (AACE)[5], threshold above which organ and pancreatic dysfunction may begin in hospitalized humans[6] and the maximum target for post-meal blood glucose in humans.[7]
Commonly used target range for diabetics, for as much of the time as possible.
<10-15 <180-270 "Renal threshold" (varies between individuals, see below), when excess glucose from the kidneys spills into the urine and roughly when the pet begins to show diabetic symptoms. See Hyperglycemia for long-term effects of high blood glucose.
14 250 Approximate maximum safe value for the highest blood sugar of the day, in dogs, who are more sensitive to high blood sugar. Dogs can go blind at this level. Cats should try to stay below this too. Check for ketones.
16.7 300 Approximate maximum safe value for the highest blood sugar of the day, in cats, to avoid neuropathy and complications. Some cats can go on long-term at this level or higher, but there will be side effects eventually. Check for ketones.
>20 >360 Check for ketones frequently, be sure you are giving insulin. Cats are much more resilient than dogs or humans at these high levels; nevertheless, the blood sugar should be lowered. The cat or dog can feel any of numerous ill effects both short and long-term, see hyperglycemia for details.

What's too high?[]

At high readings, combined with inadequate administration of insulin, and not eating or drinking enough, or an infection, animals can sometimes quickly develop diabetic ketoacidosis (DKA), which is immediately life-threatening. Always check urine for ketones at high readings. Of course, cats at much lower levels who have inadequate insulin supply coupled with infection, dehydration, or fasting can also develop ketones.

Some vets use a "sliding scale" regarding maximum permissible blood glucose values in dogs, "allowing" blind dogs or dogs with cataracts to use the concept of remaining under 250 at all times, with sighted dogs and dogs without cataracts ideally under 200.

Others apply the "under 200"[8] for dogs at all times without exceptions.

Cats are quite resilient to high blood glucose compared to dogs, and some cats lead reasonably normal lives at levels between 200 and 350 all day long. Neuropathy and other long-term effects can still build up over time, though.

Evidence from humans, mice, and in-vitro tissue studies show that damage to the pancreatic beta cells (the ones that make insulin) continues down to levels as low as 140mg/dL.[9]. This is why the AACE guidelines[10] recommend average blood sugars (for humans) of no more than 170, preferably between 65 and 136.[11]

See hyperglycemia.

Why you still need Ketostix/Ketodiastix[]

While home testing blood with a meter can tell you what your pet's blood glucose levels are, most can't do blood ketone testing.

When you have high blood glucose levels, doing ketone testing with Ketodiastix or Ketostix is good practice to make sure your pet doesn't have ketones.

In a diabetic, any urinary ketones above trace, or any increase in urinary ketone level, or trace urinary ketones plus some of the symptoms above, are cause to call an emergency vet immediately, at any hour of the day.

Renal threshold[]

The renal threshold for glucose is defined as the blood glucose level where the kidneys begin excreting excess glucose into the urine. Certain side effects on the urinary tract begin at this level, and it's also fairly close to the level where other organ damage seems to occur, though there's no actual causal relationship. This number is a bit different for every animal, and various authorities have declared it to be at different standard levels. For example:

What's normal?[]

Normal blood glucose values for non-diabetic cats and dogs[19] range from 80-150[20][21] as measured on a vet's glucometer. Home glucometers used on animals tend to read a bit lower in the below-100 ranges, (reasons not yet understood), and so will frequently show lower numbers (see chart above) that are not cause for alarm.

The Feline Diabetes Message Board FAQ[22] lists 60-120mg/dL (3.3 - 6.7 mmol/L) as "normalized" when not receiving insulin, and 60-150 (3.3-8.3) as "tightly regulated" when receiving insulin.

Diabetes being the "individual" disease it is, allows for many personal exceptions. A dog on the canine diabetes message board[23] who was tightly controlled developed hypoglycemia symptoms every time his blood sugar dropped to 85 or below. The solution was to slightly reduce his insulin which kept him at slightly higher bg levels.


Note that no single blood glucose reading is adequate to establish insulin dosage or recommended treatment. Blood glucose levels should be checked before each shot, but that alone is also not enough to determine if treatment is working. Please see curve and regulation and duration for more information on this tricky subject.

Further reading[]