is a complicated condition caused by either an absolute or
relative deficiency of insulin which results in hyperglycaemia
(elevated blood glucose levels) and glycosuria (glucose in
the urine). Diabetes mellitus is most common in older cats.
Neutered cats, male cats and obese cats are at an increased
risk of developing this condition. Genetic predisposition
to diabetes is well recognised in people, and recently there
has been evidence, particularly from Australia and New Zealand, that genetics may play a role in the development of diabetes
in cats. In these countries the Burmese breed has been identified
as being predisposed to diabetes, and analysis of pedigrees
has suggested that this is an inherited trait.
Normal actions of insulin
Insulin is produced by the pancreas which is a small organ
located in the abdomen, close to the stomach and the liver.
Insulin is released into the bloodstream where it travels
to all the tissues of the body. Its main role is to enable
cells to take up glucose (sugar) which is needed as an energy
source. Insulin also stimulates uptake of various other substances
including amino acids (building blocks for proteins), fatty
acids (needed for making cell membranes), potassium and magnesium
by tissue cells. In the liver, insulin has important roles
which include production of glycogen (a carbohydrate energy
store) and fat. Insulin also reduces the amount of glucose
made and released by the liver.
In diabetic cats, there is a relative or absolute deficiency
in insulin resulting in impaired glucose uptake by tissue
cells which causes hyperglycaemia. As the cells are starved
of glucose, they switch to using fat and protein as an energy
source. This is facilitated by breakdown of body stores of
fat and protein, resulting in weight loss and the accumulation
of toxic waste products which can precipitate a diabetic crisis
An absolute insulin deficiency may arise as a direct failure
of the pancreas to produce insulin. However, in most diabetic
cats there is a combination of insufficient insulin secretion
by the pancreas and what is known as peripheral insulin resistance.
Peripheral insulin resistance describes the situation whereby
cells of the body fail to respond to insulin as effectively
as they should. Insulin resistance can be caused by a number
of conditions including pregnancy, obesity, some drugs (eg, corticosteroids such as prednisolone, progestagens such as
megestrol acetate – ‘Ovarid';Virbac), other hormonal
conditions such as hyperadrenocorticism (tumour of the pituitary
or adrenal gland resulting in excessive production of corticosteroids
by the body) and acromegaly (a tumour producing excessive
amounts of growth hormone).
In diabetic cats, the hyperglycaemia is so severe that glucose
is excreted in the urine (glycosuria). Glucose takes water
with it so an increased volume of urine is produced (polyuria). To compensate for this,
and so that dehydration is prevented, the cat develops an
increased thirst (compensatory polydipsia). Weight loss and
a voracious appetite (polyphagia) are also frequently seen
and these may be the original reasons for presentation to
a veterinary surgeon. Therefore the main clinical signs seen
in a diabetic cat are:
• Weight loss
These signs are not always present or may pass unnoticed.
For example, the increased thirst may not be recognised if
the cat is drinking from water sources outdoors while not
noted to be drinking more in the home.
Other clinical signs which may be seen in diabetic cats include:
• Straining to pass urine and/or passing bloody urine
associated with a bacterial urinary tract infection (bacterial
• Enlargement of the liver evident on examination by
a veterinary surgeon (hepatomegaly)
• Poor coat
In a small number of diabetics, the nerves supplying the legs,
and in particular the hind legs, may be affected resulting
in a classic plantigrade stance (sunken hocks). This is caused
by a peripheral neuropathy. Very rarely, the eyes may be affected
by cataracts and retinal abnormalities which develop associated
with the diabetes. This can cause problems with vision, including
blindness in the most severely affected cats. Systemic hypertension
(high blood pressure) is a recognised potential complication
of diabetes in people and has also been reported in a small
number of diabetic cats.
Most diabetic cats will remain well in themselves but ketoacidosis
is a potential complication that can be seen in any uncontrolled
diabetic. In this situation, the cat may become extremely
depressed with signs such as vomiting, diarrhoea, complete
loss of appetite, dehydration, collapse and coma. If any of
these signs are seen in a diabetic cat, it is cause for immediate
concern and a veterinary surgeon should be contacted as soon
as possible (see later).
Diabetes mellitus is suspected in cats showing the appropriate
clinical signs but other diseases may also cause similar signs.
For example, other important causes of weight loss in an older
cat including kidney disease, cancer, hyperthyroidism (overactive
thyroid gland) and inflammatory bowel disease need to be ruled
out. The earlier that diabetes can be detected the better and so routine urine checks in cats above 7 years old are recommended.
Urine samples can be tested for the presence of glucose and ketones using special 'dip sticks' which give a rapid result |
Urine samples can be collected by using non-absorbent cat litter or aquarium gravel instead of normal cat litter
Blood and urine tests are required to confirm a diagnosis
of diabetes. Although hyperglycaemia and glycosuria are found
in diabetic cats, cats can also suffer from a stress-associated
hyperglycaemia which can cause glycosuria and therefore confuse
diagnosis. For this reason, a single blood or urine sample
cannot be considered as diagnostic of diabetes. One solution
to this problem is for the cat's owner to collect a urine
sample whilst the cat is in its non-stressful home environment.
The easiest way of doing this is to replace normal cat litter
with non-absorbent cat litter (supplied by a vet) or clean
aquarium gravel so that a sample can be collected. The urine
sample can be taken to a veterinary surgeon for testing or
the hospital may give you some test strips to use at home.
Another solution is to measure the blood levels of fructosamine
which more accurately reflects the long-term blood sugar levels
and so may help to distinguish between stress-associated hyperglycaemia
and diabetes mellitus. Fructosamine is a glycosylated serum
protein molecule which is present in higher concentrations
when the blood glucose concentration is high. An elevation
in serum fructosamine indicates that there has been significant
hyperglycaemia during the previous two to three weeks. This
test can also be used for long-term monitoring of how well
stabilised a diabetic cat receiving therapy is.
Diabetes mellitus is usually a treatable condition and although
it requires considerable dedication and commitment from owners,
it can be a very rewarding problem to manage.
Management of predisposing factors
Initial management may involve addressing factors which have
precipitated or complicated the diabetes such as treating
obesity or withdrawing drug therapy. If no predisposing causes
of the diabetes can be identified, or if correction of these
do not lead to resolution of the diabetes, then specific treatment
Dietary management of diabetes
Underweight diabetic cats may need energy dense diets until
their weight normalises. Obese diabetic cats should be put
onto a weight loss regime, under the guidance of a veterinary
surgeon, as obesity interferes with the way insulin works.
In some of these cats, this may resolve the diabetes.
Research has shown that low carbohydrate
and high protein diets can help to reduce
the requirements for insulin and improve diabetic management.
A variety of commercial petfood manufacturers produce prescription
low carbohydrate diets suitable for use in diabetic cats.
It is recommended, as far as possible, to keep the diet constant
both in terms of what is fed as well as timing of meals and
so on. Altering the feeding regime may upset the stabilisation
of the diabetes. However, it is not necessary to feed cats at strict meal times - it is fine to stick to the feeding regime that your cat is already used to.
Several different types of insulin are available. Special insulin syringes, which have very fine needles, are also shown here
In most diabetic cats, insulin therapy is required, at least initially. Insulin is given by an injection under the skin
of the scruff and most cats will be stabilised on a regime
involving either once or twice daily injections. The exact
site of administration should be changed on a daily basis
to reduce any scarring or reaction at the injection site which
may limit insulin absorption. Special insulin syringes with
very fine needles are used so that the cat will hardly feel
the injection. Veterinary surgeons often recommend that diabetic
cats are offered food just before they receive their insulin
so that the cat is distracted by eating and does not notice
There are a number of different types of insulin available
and different cats respond better to one type than another.
Intermediate (eg, lente products such as Caninsulin, an FAB Easy to Give Award winner) and long acting (eg, protamine zinc)
preparations are most commonly prescribed. There is a high
degree of individual variability but twice daily administration of insulin will be ideally required in most cats. The dose required by each cat is also very variable
and it may take several weeks to stabilise the diabetes. Many
veterinary surgeons will hospitalise diabetic cats undergoing
Insulin should be kept in a fridge at all times and a new
bottle started for each new diabetic and used for this cat
only. Before withdrawing insulin for administration, the contents
of the bottle should be gently mixed so that an even suspension
is obtained. Excessively vigorous agitation can damage the
fragile insulin chains reducing the strength of the suspension.
Insulin doses are measured in units with most preparations
consisting of either 40 or 100 units per ml. Where possible,
insulin syringes should be used since these are calibrated
in units and therefore enable accurate measurement of the
insulin required. 100 unit and 40 unit syringes are commercially
available. In some cases, the cat may be prescribed an extremely
low dose of insulin in which case a diluted insulin preparation
can be made using sterile water for injection or saline. This
should be prepared by a veterinary surgeon and replaced every
2 – 4 weeks. The diluted preparation of insulin should
be stored and handled as already described for insulin.
Glucometers such as this are frequently used in assessment of diabetic cats as they only take a few seconds to measure the blood glucose levels in a single drop of blood
A strict routine is essential for the stabilisation of any
diabetic cat. Whilst the cat is in hospital, it will be closely
monitored so that if the treatment is not adequate this can
be changed. Initial stabilisation usually takes between a
few days and a couple of weeks. During this period, several
parameters are monitored:
• Demeanour: Most diabetic cats appear
very bright and well. In ketoacidosis, one major complication
of uncontrolled diabetes, the cats can become very depressed
and may show other signs such as vomiting, diarrhoea, panting,
dehydration and collapse. In severe cases, death can occur
rapidly so it is important to act quickly (see later under
section on ketoacidosis).
• Appetite: Almost all diabetic cats have a voracious
appetite and this usually persists in spite of good stabilisation
of their diabetes.
• Water intake: This is a useful thing
to monitor since diabetic cats are usually very thirsty. A
reduction in daily water consumption should be seen as the
diabetes is controlled. Normal daily (24 hours) water consumption
in cats receiving moist food is around 10 - 20 ml per kg bodyweight.
• Urinalysis: Urine glucose monitoring
is of some value in that the extent of glycosuria can be determined
although morning urine samples often contain large amounts
of glucose even in well-controlled diabetics. For this reason,
urine glucose monitoring alone is not considered adequate
in the management of diabetic cats. Urinalysis also allows
detection of urinary tract infections (by sediment examination
or urine culture) and the detection of ketones which are an
important indication of poor diabetic control needing immediate
action (see later).
• Blood glucose measurements: Serial
blood glucose measurements allow the best monitoring of a
diabetic cat. The only situation in which this does not apply
is those cats where stress-associated hyperglycaemia is a
problem. In some of these cats, withdrawal of blood through
an indwelling intravenous catheter may help to reduce stress.
The main aims of blood glucose monitoring are:
- To determine the time of peak action
of the insulin.
- To determine the duration of the insulin's
action. This tells you if the insulin the cat is receiving
is lasting long enough or whether a different preparation
of insulin, or more frequent injections may be appropriate.
- To determine the trough glucose measurement.
This is the lowest the blood glucose levels fall after insulin
is given. In the ideal situation, the blood glucose falls
to around 5 - 9 mmol/l and spends the majority of the 24
hour period below 14 mmol/l. If an insufficient response
to insulin is seen, a higher dose may be required.
is important that the blood glucose levels are not reduced
too low (hypoglycaemia, less than 4 mmol/l is risky) as this
can cause severe illness or death (see later section on hypoglycaemia).
If this is the case then the dose of insulin needs to be reduced.
It may be acceptable to take a few strategically timed blood
samples over the day to avoid over-frequent sampling. For
example this would include a sample prior to insulin administration
then several samples around the time of the insulin's peak
action. The insulin regime can be altered based on these results
and once it is thought to be appropriate, a 24 hour blood
glucose curve may be performed in order to monitor more closely
what is happening. Samples are taken periodically (usually
every one to two hours) throughout the day until the blood
glucose returns to its pre-insulin levels. The information
gained indicates the insulin duration and peak action. Where
it is necessary to alter the dose of insulin, this is normally
done slowly, ie, the dose is increased no more frequently
than every third day since cumulation of insulin can be seen
with sudden signs of insulin overdose. Hypoglycaemia results
and this can have fatal consequences (see later section on
this for more information).
• Weight: It is important to monitor
this since uncontrolled diabetes can result in severe weight
loss. With good stabilisation, underweight diabetic cats should
gain weight – it is important to ensure that these cats
do not become overweight as their condition improves! As stated
earlier, a weight loss regime should be employed in those
diabetic cats that are overweight.
Once the diabetic patient is stabilised within the hospital,
it may return home under the care of its owner. Care of a
diabetic cat requires considerable dedication.
Care of the diabetic cat at home
Owners of a diabetic cat must be aware of the importance of
a strict routine in care of their diabetic. Insulin injection
techniques can be taught at the hospital using sterile saline.
Timing of insulin injections can initially be altered to suit
an owner's lifestyle but they must then be kept as constant as possible.
Knowledge on correct insulin storage, handling and administration
is required. The dose of insulin given should never
be changed without consulting a veterinary surgeon. One of the most common reasons for poor stabilisation at home
is problems with insulin storage or administration.
On discharge from the hospital, owners should be informed
of what the normal pattern for their cat whilst stable in
the hospital is in terms of demeanour, daily water consumption
etc. If possible, a diary recording the following details
should be kept:
• Time of insulin injection/s
• Dose of insulin injected
• Amount of food offered and eaten (and time of feeding
if food is not offered ad libitum)
• Amount of water drunk over a 24 hour period
Additional monitoring of glucose and ketone levels in urine
samples collected overnight may also be advised (see section
on Diagnosis for information on collecting a urine sample).
A small amount of day to day variation in the amount of glucose
present in the urine is not cause for concern but if large
changes are seen or if ketones are detected, a veterinary
surgeon should be contacted (see later). If possible, weekly
weighing is helpful.
Urgent causes for concern
It is important to be aware of what constitutes a problem,
when veterinary advice needs to be sought and when urgent
action is required.
It is sensible to obtain some glucose powder in case your diabetic cat sufers from low blood sugar (hypoglycaemia) at any time. Also shown is glucose solution which can be given by injection, by a veterinary surgeon, in severely affected cases
most life-threatening complication that can occur at home
is hypoglycaemia (low blood glucose levels). This is seen
when blood glucose levels fall below about 3 mmol/l. Hypoglycaemia
can occur if an insulin overdose is given or if there are
problems with the insulin regime, eg, insulin lasting more
than 24 hours leading to a cumulative effect over a period
of days. The main signs of hypoglycaemia are (in order of
• Drunken gait (ataxia)
• Strange behaviour, eg, aimless wandering, searching
for food, licking lips
• Severe neurological signs, eg, collapse, convulsions,
loss of consciousness and eventually death
Rapid recognition and treatment of hypoglycaemia is needed
to prevent progression to the severe signs and death. If the
signs are mild, then the cat should be offered food and encouraged
to eat. If this is not successful or if the signs present
are more severe, for example in cats that are collapsed or
unable to swallow, then glucose powders or syrups should be
given orally, applied directly to the gums. A notable effect
should be seen within five minutes of applying a tablespoon
of glucose to the gums. If no glucose powder or syrup is available
then honey or sugar should be used. Owners should then contact
the surgery for further advice. Severely hypoglycaemic cats
may need to be admitted for intravenous glucose administration
and further stabilisation.
All owners should keep a supply of oral glucose powder
or syrup at home so that this can be given if required. These
are available from chemists or from veterinary surgeons.
Ketoacidosis is an uncommon complication of poorly controlled
diabetes. It can be rapidly fatal if not treated so requires immediate action where suspected. The clinical signs most
frequently seen with ketoacidosis are:
• Loss of appetite
The breath may have a fruity odour (pear drops). Owners of
diabetic cats should be provided with urine glucose and ketone
sticks by their veterinary surgeon to allow periodic monitoring
of the urine. This should be done as part of the normal routine
(once or twice a week initially) or if there is any suspicion
of ketoacidosis, for example if any of the above clinical
signs are seen in a previously well diabetic cat. Ketoacidosis
can also be confirmed by demonstrating the presence of ketones
in the saliva, tears or blood using reagent strips.
If a positive ketone result is seen, immediate veterinary
advice should be sought. This rule applies even if the cat
seems quite well in itself. Ketotic cats require immediate
intensive treatment with insulin given intravenously or intramuscularly
for a rapid effect to regain control of the diabetes. In addition
to this other treatments including intravenous fluid therapy,
antibiotics and bicarbonate may be required. Treatment for
ketoacidosis usually requires hospitalisation.
Additional causes for concern
Large variations in any of the things being monitored (food
and water intake, demeanour, urinalysis results, etc) are
generally a cause for concern and should be investigated.
These may indicate poor control of the diabetes (eg, inadequate
dose of insulin), mild ketoacidosis or presence of other diseases
which complicate the control of the diabetes. If any of these
are seen, a veterinary surgeon should be consulted for advice.
Initially all diabetic cats should be seen every one to two
weeks to assess how well their diabetes is controlled and
to weigh them. It is not uncommon for problems to be seen
in the early stages of care of the diabetic at home. These
are often related to the storage and administration of insulin
so are usually quite easy to identify and remedy. Common problems
• Routine not adhered to, eg, insulin given at a different
time each day
• Variable quantity or type of food being fed
• Incorrect insulin storage
• Incorrect insulin mixing/injection technique
Your vet may ask you to demonstrate how you mix and inject
insulin in order to check that this is being done correctly.
If these problems are eliminated as a cause of the poor stabilisation,
then further investigations may be needed to locate the problem
so that this can be remedied. In some cases it will be necessary
to re-admit the cat for more detailed assessment which may
include a 24 hour glucose curve. Possible causes of poor stabilisation
• Concurrent disease, eg, other hormonal diseases, pancreatitis,
• Infections - most commonly urinary tract, mouth and
• Persistent ketoacidosis (see earlier)
• Inappropriate insulin dose/preparation
In well controlled diabetics, less frequent monitoring may
be sufficient although this should not fall below once every
three to six months at which time a new bottle of insulin should
be started. At these check-ups a 24 hour blood glucose curve
should be done in order to critically assess the regime and
the cat should be weighed.
The long-term outlook for cats with diabetes mellitus varies
according to how old they are, how easy it is to stabilise
their diabetes, whether they have any other diseases and how
severe these are. In one study, the average survival time
for diabetic cats was around 2 years. Many diabetic cats have
an excellent quality of life and are extremely rewarding cases
Further guidance for owners addressing the practicalities of dealing with a diabetic cat is given in 'Diabetes: what does it mean for my cat and me?'
Updated November 2008