Diabetes mellitus strikes 1 in 400
cats and a
similar number of dogs. Symptoms in dogs and cats are similar to those
in humans. Generally, most dogs and about half of cats experience type-1
(insulin-dependent) diabetes, rather than the type-2 that's now becoming
common in obese humans. The condition is definitely treatable, and need
not shorten the animal's life span or life quality. In cats, prompt
effective treatment can even lead to diabetic remission, in which the
cat no longer needs injected insulin. Untreated, the condition leads to
blindness in dogs, increasingly weak legs in cats, and eventually
malnutrition, ketoacidosis and/or dehydration, and death.
Cats and dogs will generally show a gradual onset of the disease over a few
weeks, and it may escape notice for a while. The condition is unusual in animals
less than 7 years old. The first obvious symptoms are a sudden weight loss or
gain, accompanied by excessive drinking and urination. Appetite is suddenly
either ravenous (up to 3 times normal) or absent. In dogs, the next symptom is
vision problems and
cataracts, while in cats the back legs will become weak and the gait may become
stilted or wobbly. A quick test at this point can be done using keto/glucose
strips (the same as used on the Atkins diet) with your pet. If the keto/glucose strips show glucose in the urine,
diabetes is indicated. If a strip shows ketones in the urine, the pet should be
brought to an emergency clinic right away.
Watch for noticeable thinning of the skin and apparent fragility -- these are
also serious and indicate that the pet is consuming all its body fat.
Dehydration is also common by this point, and death can follow quickly.
Diabetes can be treated but is life-threatening if left alone. Early
diagnosis and treatment by a qualified veterinarian can help, not only in
preventing nerve damage, but in some cases, in cats, can even lead to remission.
Diet is a critical component of treatment, and is in many cases effective on
its own. For example, a recent mini-study
showed that many diabetic cats stopped needing insulin after changing to a
low-carbohydrate diet. The rationale is that a low-carb diet reduces the amount
of insulin needed and keeps the variation in blood sugar low and easier to
predict. Also, fats and proteins are, in dogs and perhaps cats, turned into
blood glucose much more slowly and evenly than carbohydrates, reducing
blood-sugar highs right after mealtimes.
Latest veterinary good practise is to recommend a low-carb diet for cats, and
a high-fiber, moderate-carb diet for dogs. In dogs another alternative is to
feed a normal healthy diet but give mealtime insulin bolus supplements.
It's now becoming clear that lower carbohydrate diets will significantly
lower insulin requirements for diabetic cats. Carbohydrate levels are highest in
dry cat foods (even the expensive prescription types) so cats are best off
usually with a low-carb healthy canned diet. Some prescription canned foods made
for diabetic cats are effective, but some ordinary ones work just as well.
Between 3 and 9% calories from carbohydrates seems to be optimal.
These lists of common commercial cat foods and their carbohydrate energy content
are kept up-to date.
Oral medications like Glipizide that stimulate the pancreas promoting insulin
release, (or in some cases, reduce glucose production) work in some small
proportion of cats (Most dogs are Type I diabetics so oral hypoglycemic drugs
are usually not prescribed for them), but these drugs may be completely
ineffective if the pancreas is not working. Worse, these drugs have been shown
in some studies
to damage the pancreas further, reducing the chances of remission for cats. They
have also been shown to cause liver damage. Many are reluctant to switch from
pills to insulin injections, but the fear is unjustified; the difference in cost
and convenience is minor, (many cats are easier to inject than to pill!) and
injections are more effective in almost all cases.
Humans with Type-1 diabetes are often treated with a "basal plus bolus"
method, where a long-acting insulin is injected once or twice daily to provide a
"basal" insulin level, then shorter-acting insulin is used just before
mealtimes. For cats and dogs a "basal" method is usually employed instead -- a
single slow-acting dose, twice daily, attempts to keep the blood sugar within a
recommended range for the entire day. In this case it's important for the pet to
avoid large meals, since they can seriously affect the blood sugar. (Meals may
also be timed to coincide with peak insulin activity.) Once-daily doses are not
recommended for most cats, since insulin usually metabolizes faster in cats than
in dogs or humans; an insulin brand that lasts 24 hours in people may only be
good for about 12 in a cat.
Cats and dogs may be treated with animal insulins (pork-based seems to work
best in dogs, beef-based in cats), or with human synthetic insulins. The best
choice of insulin brand and type varies between pets and may require some
experimentation. One of the popular human synthetic insulins, Humulin N /Novolin
N/ NPH, is reasonable for dogs, but is usually a poor choice for cats, since
cats' metabolisms run about twice as fast. The Lente and Ultralente versions
were therefore very popular for feline use until summer 2005, when Eli Lilly and
Novo Nordisk both discontinued them.
Until the early 1990's, the most recommended type for pets was
PZI, but that type was phased out over the 1990's and is now difficult to
find in many countries. There are sources in the US and UK, and many vets are
now starting to recommend them again for pets.
, known in the USA as Vetsulin
, made by Intervet
 (owned by
is a brand of pork-based insulin, which is designed for cats and dogs, and is
available both through veterinarians and pharmacies with a veterinarian's
prescription, depending on the country
. Although not approved, Caninsulin can also used for the treatment of
diabetes mellitus in pet rabbits
 and guinea pigs.
Two new ultra-slow time-release synthetic human insulins are just becoming
available in 2004 and 2005 for improving basal stability, generically known as
Insulin Detemir ("Levemir")
and Insulin Glargine ("Lantus"). A mini-study at the University of Brisbane,
has had remarkable results with Insulin Glargine in cats. No studies have yet
been performed on pets with Detemir/Levemir, but early anecdotal evidence
shows that it is also very effective on cats.
Neuropathy in cats
The weak legs syndrome found in many diabetic cats is a form of
neuropathy, in particular caused by damage to the myelin sheath of the
peripheral nerves caused by glucose toxicity and cell starvation. (There are
other conditions that can cause weak legs too, consult your vet before assuming
neuropathy.) Most common in cats, the back legs become weaker until the cat
displays "Plantigrade stance", standing on its hocks instead of on its toes as
usual. The cat may also have trouble walking and jumping, and may need to sit
down after a few steps. Some recommend a form of vitamin B12 called
methylcobalamin to heal the nerve damage. Neuropathy often heals on its own
within 1 to 3 months once blood sugar is regulated, but anecdotal evidence
points to a faster recovery rate with these
Dosage and regulation
Cats and dogs may in some cases have their mealtimes strictly scheduled and
planned to match with injection times. In other cases where the pet free-feeds
and normally eats little bits all day or night, it may be best to remain on this
schedule and try to use a very slow-acting insulin to keep a constant level of
blood glucose. Consult your veterinarian. Note that some veterinarians still use
the outdated recommendation of using Humulin "N" or NPH insulin for cats. This
insulin is too fast-acting for most cats (though fine for dogs and humans). Cat
metabolism runs about twice as fast as human, and the often-effective
slower-acting Lente and Ultralente (Humulin L and Humulin U) insulins are being
discontinued (as of 2005), so most cats are now using either the veterinary PZI
insulins, or the new full-day analogs glargine (Lantus) and detemir (Levemir).
The goal at first is to "regulate" the pet's blood glucose, which may take a
few weeks or even many months. This process is basically the same as in type-1
diabetic humans. The goal is to keep the blood glucose values in a comfortable
range for the pet during the whole day, or most of it.
Have an initial blood curve taken over 24 hours at the vet and receive
an initial dosage recommendation.
The initial dosage will be very conservative (low) (usually between 0.5
and 2 units daily, split into 12-hour dosages) and may not affect the pet's
symptoms noticeably at first. This is necessary because although high blood
sugar can kill within weeks, low blood sugar can kill in minutes. Dosage
must be increased gradually and carefully. The usual recommended method is
to increase the dose by 1/2 to 1 unit every 7 to 14 days, followed by
further glucose testing. An initial decrease may also be necessary --
it is fairly common for the initial recommendation to be a little bit too
high, especially if it was estimated by weight. See
Chronic Somogyi Rebound below. Buying an inexpensive blood
glucose meter and testing for yourself just before each shot and at
midpoint is essential -- it will save many expensive trips to the vet, avoid
dangerous overdoses, and give you a better handle on the pet's ongoing
condition. Urine strips are not accurate enough for this.
Your pet is "regulated" when its blood glucose remains within an
acceptable range all day, every day. Acceptable varies somewhat between
cats, dogs, and vets, but is roughly from 5 to 16.7 mmol/L (90 to 300 mg/mL
in the USA) for cats, and between 5 and 14 (90 to 250) for dogs. (The range
is wider for diabetic animals than non-diabetic, since shots cannot
replicate the accuracy of a working pancreas.) It's important, though,
that the glucose level be in the lower half of that range for as much of the
day as possible. If you are not doing home glucose testing, some vets
recommend that you stop increasing the dosage when the dog or cat is
drinking normally, urinating normally, and eating normally, although organ
damage may continue in some cases until glucose is below the "Renal
Threshold" -- testing urine with keto/glucostix will show when this has been
Obstacles to regulation:
Sometimes your pet will suddenly appear to need less insulin than
before. If this happens (their blood sugar will go lower than usual one
day), drop the dose immediately and call your vet. If testing just
before an injection, and the reading is much lower than expected, it may
be wisest to skip that dose and continue retesting every 2-3 hours. If
the drop is dramatic and leads to a hypoglycemic episode (see below),
the cat's sensativit to insulin may increase dramatically. You should
consider dropping their dose after consulting your veterinarian, and
raise it only by half to one unit per 5-7 days, as before.
Sometimes your pet's blood sugar will suddenly seem much higher than
usual. This is often not a good time to increase their insulin
dosage -- quite the opposite. It often indicates that a low blood sugar
condition (or rapid sugar drop) was experienced a few hours before, and
Somogyi rebound is in progress. To be sure, drop the next dose by
15%-50% and take glucose readings every 4 to 8 hours until the glucose
levels out. Then wait a few more days for the Somogyi hormones to
decrease in the body, and then you can increase again by 0.5-unit steps
every 5-7 days. If you experienced this rebound, chances are that your
original dose was too high, so you should try to find an ideal dose at a
Chronic overdose masked by Somogyi: A dose that is fractionally too
high can easily cause a Somogyi rebound, which can look like a need for
more insulin. This condition can continue for days or weeks, and it's
very hard on the cat's metabolism. See more on this topic in the Somogyi
High-carb cat/dog food: Many commercial foods (especially "Light"
foods) are extremely high in cereals and therefore carbohydrates. The
extra carbohydrates will keep the cat or dog's blood sugar high, and if
you're free-feeding may also make the blood sugar curve over the course
of the day unpredictable. In general, canned foods are lower in
carbohydrates than dry ones, and canned "kitten" foods lower still.
show that cats' diabetes can be better regulated and even sometimes
cured with a low-carbohydrate diet. This may not apply to dogs. If
switching to a lower-carbohydrate food, do it gradually and lower the
insulin dosage appropriately, with your vet's help. If your cat is on a
special diet for pancreatitis, chronic renal failure, or any other
condition, consult your vet for the appropriate diet for that condition
Wrong insulin: Different brands and types of insulin have
idiosyncratic effects on different cats and dogs. If you've settled on a
dose that seems to keep the pet's blood sugar within range at peak
effectiveness, but the sugar readings remain dangerously high at shot
times, the insulin may not be lasting long enough for your pet, or may
not be the best choice. Switching to a slower-acting or a
better-tolerated insulin for that pet, and lowering the dose initially
to be safe, may be the next step.
Blood sugar guidelines
Absolute numbers vary between pets, and with meter calibrations. The numbers
below are as shown on a typical home glucometer, not necessarily the more
accurate numbers a vet would see. For general guidelines only, the levels to
watch are approximately:
this is an average non-diabetic pet's level, but leaves little
margin of safety for a diabetic.
a common minimum safe value for the lowest blood sugar of the day
desired range for diabetics (non-diabetic range is 2.2 - 7.5,
(40-130) but usually unsafe to aim for)
threshold" (varies between individuals) excess glucose from the
kidneys spills into the urine, pet begins to show diabetic symptoms.
Long term damage to eyes, nerves, pancreas and other organs if
glucose remains above here too often. Risk of
Urinary tract infection over time.
approximate maximum safe value for the highest blood sugar of the
day, in dogs, to avoid short-term eye damage.
approximate maximum safe value for the highest blood sugar of the
day, in cats, to avoid short-term nerve damage.
At high readings like this, combined with an infection, dehydration,
or a fast, animals can sometimes quickly develop
Diabetic ketoacidosis which is immediately life-threatening. Always
check urine for ketones at high readings.
The regulation process is described in more detail
Detecting and avoiding chronic somogyi rebound
It's confusing but true: Too little insulin means pre-shots are too high; too
much insulin often also means pre-shots are too high. This effect is often noted
by those who test their pets' blood glucose at home.
The reason: Anytime the glucose level drops too far or too fast, the cat or
dog may defensively dump glucose (converted from glycogen in the liver), as well
as hormones epinephrine and cortisol, into the bloodstream. (If these are
insufficient, hypoglycemia ensues!) The glycogen raises the blood glucose, the
other two may make the pet insulin-resistant for a day or two. This phenomenon
was first documented by a Dr. Somogyi.
Even when raising the insulin dose slowly and carefully, it's possible to
pass the correct dose and go on to an overdose. (A typical case is increasing
bidaily dosage from 1 unit to 2, passing a correct dose of 1.5 units.) This may
produce a rebound -- a swift jump in blood glucose up from a dangerously low
reading, to beyond the previous pre-shot level. The pet may be a bit less
responsive to the same dose the next shot, from those other hormones. Repeating
the overdose on subsequent days, and checking only pre-shot readings or urine
glucose, can give the dangerously wrong impression that more insulin is needed!
Remember to check occasionally at the expected nadir (low point) as well.
It's unusual to be monitoring glucose right when this happens, and typical to
just continue the overdose, leading to a repeated rebound situation. So it's
good to learn to recognize the patterns of repeated rebound.
A typical rebound pattern, most often seen with long-acting insulins, is
a high, flat, unresponsive blood sugar over a period of days. Sometimes,
often when raising dosage, this high flat curve will be punctuated by sudden
drops to very low values, (with possible hypoglycemic events) followed by a
fast return to high unresponsive numbers. (It's the sudden dip that
distinguishes this pattern from inadequate insulin!)
When using shorter-acting insulins, repeated Somogyi rebound may
manifest instead as rapidly alternating high and low blood sugar numbers
with no apparent logic. The highs and lows will both be exaggerated compared
to what you'd see on a smaller dose.
According to recent experience on internet diabetes forums, the rebound
phenomenon may be less dramatic and more common than usually thought, in some
pets. The term "mini-rebound" is beginning to gain currency. If your insulin
dose is just a smidgen high, you may see either nothing at all, or a
hypoglycemic episode or a mini-rebound. Some
Feline Diabetes Message Board regulars describe mini-rebounds here:
It's not always easy to tell a rebound from a regular curve showing insulin
action ending normally. One way to tell the difference is to take a "curve"
(repeated tests every 2 hours starting with the insulin shot) on a weekend and
look for the shape of the curve. If the curve is valley-shaped, and gradual,
then you are not seeing Somogyi rebound. Other shapes should arouse suspicion.
In particular, if the rise after peak action is faster and rises higher than the
original pre-insulin level and the original fall in blood sugar, you have good
cause to consider rebound. The only sure way to check is to reduce dosage and
look for a better-shaped curve.
A fairly sure sign: Anytime blood glucose numbers seem higher after
dosage is raised, consider the possibility of a somogyi rebound. But other
things can cause unexpectedly high blood glucose too, so look for a clear
correlation with dosage changes.
An acute hypoglycemic episode (very low blood sugar) can happen even if you
are careful, since pets' insulin requirements sometimes change without warning.
The symptoms are depression/lethargy, confusion/dizziness, loss of
excretory/bladder control, vomiting, and then loss of consciousness and/or
seizures. As soon as possible, administer honey or corn syrup by rubbing it on
the gums (even if unconscious, but not if in seizures), and rush it to the vet.
Carry more honey or corn syrup with you on the way and keep rubbing it on the
gums, where it can be absorbed -- it could save the pet's life. Every minute
without blood sugar causes brain damage. (Some recommend administering syrup
anally if the animal is in seizures!)
If the pet has hypoglycemia according to the blood glucose meter (<2.2mmol/L
or 40mg/dL), but no symptoms, give treats or food if possible. If they won't
eat, try putting food in their mouth. If that doesn't work, administer some
honey followed by food or cat treats, and continue to do so until the blood
glucose is rising, and the latest insulin shot's peak action is past.
Sometimes a mild hypoglycemic episode will go unnoticed, or leave evidence
such as an "accident" where kitty fails to make it to the litterbox. In these
cases the blood sugar will probably appear paradoxically high upon the
next test hours later, since the pet's body will react to the low blood sugar by
stimulating the liver to release stored
This condition is known as Somogyi rebound (see link above), and
requires a lowered insulin dosage for the next few days. The
Somogyi rebound may also occur when the pet's blood glucose drops too rapidly,
even if it never actually reaches a low reading.
Remission in cats
It is in many cases possible to induce remission (a temporary or permanent
freedom from insulin-dependence) in diabetic cats. (This appears to be unique to
cats, unfortunately for dogs and humans.) There is growing agreement among
that a combination of low-carb healthy diet, well-chosen insulin, and
well-chosen dosage plans can in many cases heal a damaged pancreas and allow the
cat's blood sugar to be controlled entirely by diet thereafter. (A low-carb diet
is usually required for the remainder of the cat's life.)
Remission can be induced in 20, 30, or even over 70 percent of cats who are
properly regulated quickly. Chances of success are highest in the first few
months after initial diagnosis. This limited time window is a good reason to
start with low-carb diet and very slow-acting insulins, the most successful
known combination, right away.
An explanation can be pieced together from recent studies
 in which diabetes in cats is perpetuated, if not always caused, by a
combination of glucose toxicity and
amyloidosis , such that the insulin-producing islets of the pancreas become
clogged with amyloid deposits. Cats may present with type-2 (insulin-resistant)
diabetes, at least at first, but hyperglycemia, left untreated, will damage the
pancreas over time and induce type-1 diabetes as well.
Amylin (aka IAPP) is normally produced in the Islets of Langerhans along with
insulin, as a response to high blood sugar. In a damaged pancreas, little
insulin is made, but amylin continues to be produced. Lack of insulin leads to
further hyperglycemia which stimulates higher amylin production, some of which
remains lining the islets. Oxidization caused by excess glucose denatures the amylin (as well as some vital proteins in the Islets),
which congeals and thickens the deposited amylin into amyloid, which clogs the
islets more effectively. Once the islets are blocked, insulin production is
blocked. Once this happens to most of the pancreas, remission is no longer
Note that Glipizide and similar oral diabetic medicines have been shown to
increase amyloid production and amyloidosis.