Diabetes mellitus is a disease in which not enough
insulin is produced by the pancreas, or the cat’s body cells do not
properly process insulin which the pancreas has produced. Insulin is
a hormone which enables the body to process food and to produce energy
from it. If this mechanism is faulty, the cat develops hyperglycaemia
(high blood sugar levels), which eventually leads to high sugar levels in the
urine (glucosuria).
There are two forms of diabetes mellitus, uncomplicated
and diabetes with ketoacidosis. Cats with the former may only have mild
symptoms, at least in the early stages, but cats with ketoacidosis are
usually very ill, and may die if not treated promptly.
Obesity in cats, as in humans, is a strong
predisposing factor for diabetes.
Cats who are on
corticosteroids may also develop diabetes, but this may disappear once
the steroids are stopped (which should always be done gradually). Going
into remission is relatively common in cats with well controlled diabetes,
even if they are not on steroids.
Predictors of clinical remission in cats with
diabetes mellitus (2010) Zini E, Hafner M, Franchini M,
Ackermann M, Lutz TA & Reusch CE Journal of Veterinary Internal
Medicine24(6) pp 1313-21 found that 50% of cats in the study
went into remission and that this was more common in older cats.
The increase in sugar in the urine causes
polyuria
(increased urination) and
polydipsia (increased drinking).
Diabetic cats also tend to lose weight, so to some extent the
symptoms of diabetes may resemble those of CKD, although there is one
noticeable difference, namely that diabetic cats tend not to lose their
appetites – they lose weight despite continuing to eat, and may in fact
eat more (this
can also be a symptom of
hyperthyroidism).
However, more advanced diabetes may cause lack of appetite,
plus poor coat
quality, vomiting and dehydration and occasionally breathing problems.
Bladder infections are also relatively common because of the sugar in the
urine, and inappropriate elimination may occur.
You may
also see a plantigrade posture (as demonstrated by
Ollie to the left), where the cat walks on his/her hocks
instead of his/her feet: this is most common in diabetic cats,
caused by diabetic neuropathy, where the nerves in the legs are damaged by
the disease,
but may
sometimes be seen in cats with high phosphorus levels,
or with neurological problems from other causes.
Ollie did this because of
low
potassium levels. Since Ollie is so fluffy, you may find this photo on
123catworldclearer.
Long Beach Animal Hospital has a photograph of a cat with
diabetic neuropathy doing this (click on Symptoms).
Newman Veterinary
has a good before and after photo of a diabetic cat with this
problem, scroll down a little to Other Common Consequences, then click on
Plantigrade Stance (in red font).
The Mayo Clinic has information about
peripheral neuropathy, including that caused by diabetes.
The vet will base the diagnosis on bloodwork, clinical
signs, and high levels of sugar in the blood and urine on an ongoing
basis. Cats who are stressed by vet visits may sometimes have high blood
glucose levels, so this is not necessarily a definite sign of diabetes, it
is the ongoing nature of the
increased
glucose level
that
is important. For this reason, it is a good idea to check fructosamine, which measures
concentrations of glucose molecules historically over a period of
approximately 2-3 weeks. Lab
Tests Online has an overview of the fructosamine test.
Cats with ketoacidosis may have elevated BUN and
creatinine levels, which in this situation may not necessarily be a sign
of CKD, particularly if phosphorus and potassium levels are normal.
Diabetic cats also often have dilute urine unrelated to CKD, and the
resulting dehydration may also cause increased kidney values. Once the
diabetes is under control, the BUN and creatinine levels may improve.
Initially t
he bloodwork may
also indicate liver damage, which
should improve as the diabetes is brought under control.
Cats with ketoacidotic diabetes normally require
hospitalisation including IV fluids and insulin therapy, until they are
stabilised; thereafter they will be treated as cats with uncomplicated
diabetes.
Cats with diabetic neuropathy often benefit from
Vitamin B12 in the form of
methylcobalamin.
Jasper's Page has more information on
this treatment.
Controlling any infection
that is present, such as a urinary
tract infection, may make the diabetes easier to control.
Insulin
Uncomplicated diabetes is usually managed by means of
insulin injections. Bovine insulin is most similar genetically to feline
insulin, and is readily available in the UK; however, in the USA
animal-based insulins are often imported from the UK and may be relatively
expensive. The
insulin
is administered once or twice daily, and cats vary in their
response, so the amount and the frequency are determined by checking blood
glucose levels. This needs to be done every few hours at first and may be
done in hospital initially, but gradually the frequency
of
checks
can be reduced to once or twice a day (see
monitoring). If the diabetes is properly controlled, the earlier
symptoms should disappear.
Cornell University College of Veterinary Medicine
has a series of videos covering all aspects of diabetic cat care, including
how to give insulin, monitoring your cat, and recognising and treating
hypoglycaemia.
Oral Medication
Sometimes diabetic cats can be treated with an oral
medication called glipizide instead of injectable insulin. However,
only about 30% of diabetic cats respond to glipizide, and cats taking it
must be carefully monitored because the drug can damage the liver.
In any event, most cats are far easier to inject than to pill.
Diet
Diabetic cats also require their diet to be monitored.
Your vet can advise you on frequency of feeding, but
usually cats receiving insulin twice a day are fed half their daily food
ration each time; free feeding is not normally appropriate for diabetic
cats. Cats receiving glipizide
are normally fed several small meals a day.
High fibre, high complex carbohydrate diets
(such
as Hill’s w/d diet)
are
sometimes recommended for diabetic cats because it used to be believed that they might
help to control blood glucose levels. However, cats have a low natural
requirement for carbohydrates, and more
recent research in fact indicates that higher protein, higher fat
and lower carbohydrate diets may be more suitable for diabetic cats. Suitable foods for this approach include
Purina DM Dietetic Management
veterinary formula (not currently available in UK), and kitten foods, which are usually
high in protein and fat. Hill's have a similar food
called
m/d (click on Prescription Diet,
then on Cat, then on m/d), which also has a relatively
low phosphorus level of 0.7% on a dry matter analysis basis. It is
important to try to moderate
phosphorus
intake for cats with both CKD and diabetes, and if necessary, phosphorus
binders will need to be used.
ome diabetic cats are so sensitive to carbohydrate that
they need less insulin, or in a few cases stop needing it all together,
when switched to a low carbohydrate diet. Generally speaking, canned foods
are much lower in carbohydrate than dry foods, so canned foods low in cereals and added
sugars may be helpful in such cases, but dry foods may be less suitable because they
tend to have
a high carbohydrate content.
Diet changes should be made
gradually if a cat is already taking insulin, and blood glucose levels should
be carefully monitored, because sometimes there is a dramatic drop in blood glucose in
response to reduced carbohydrate, with a possible risk of an overdose of
insulin (see
hypoglycaemia).
Urine glucose is only really useful for initial
diagnosis – healthy cats do not have glucose in their urine – because it
is too imprecise a measure to make proper decisions about insulin dosage.
However, you will probably need to check
urine ketone levels using dipsticks
(Ketostix, available from pharmacies). Even a trace of
ketones is a cause for concern and warrants an immediate vet visit.
Home Blood Glucose Testing
You will also need to monitor your cat's blood sugar levels, and may wish
to do this at home using a glucometer
(available
from pharmacies for use by human diabetics)
– home monitoring is much cheaper for you and less stressful for your cat. The blood can
normally be taken from the ear (make sure it is warm) using
a sterile lancet, and only a tiny amount is required, though many
UK vets are unfamiliar
with this approach. Generally speaking, a cat is considered regulated if
his/her
blood glucose consistently remains in the 5-15 mmol/l (US: 100-300 mg/dl)
range.
Sometimes cats
are started on too high a dose of insulin, which leads to a sudden drop in
blood sugar levels, and the body reacts to this by releasing glucagons
which raise blood sugar levels again. It thus appears, based on spot
checks at the vet's, that the cat requires even more insulin, when in fact
the opposite is the case. This is known as the Somogyi Effect. Home blood
glucose monitoring gives more accurate results and can help you to avoid
such problems.
Veterinary Partner has step by step
instructions for home blood glucose testing with
As a general rule,
too much insulin is far more dangerous for a diabetic cat than too little,
and may cause low blood sugar (hypoglycaemia). Symptoms include weakness, lack of co-ordination, convulsions and coma.
The cat should be offered food immediately if still able to eat, or you
may need to rub corn syrup
or
powdered glucose
on the
gums (in UK you can also buy a human OTC diabetic product called Hypo-Stop); otherwise you should contact your vet
urgently. You will need to discuss your treatment programme with your vet following an incident of hypoglycaemia.
If you are dealing
with both diabetes and CKD, it is more important that the diabetes should
be regulated, and in fact once this is achieved, you may find the CKD
improves too. Please also see
diagnosis above.
People dealing with both diabetes
and CKD are sometimes anxious because it appears that the protein
requirements of the two conditions are incompatible, but in fact low
protein is not necessarily essential in the treatment of CKD, see
Nutritional Requirements and
diabetes diet for more information.
A dehydrated
cat may respond less well to insulin, and many people have found that once sub-Qs are begun, the insulin seems to
work more effectively, sometimes with longer duration than was previously
the case.
Anecdotal evidence suggests that diabetic cats with
CKD
may do less well on
benazepril
(Fortekor) than cats with CKD only.
Cornell University College of Veterinary Medicine
has a series of videos covering all aspects of diabetic cat care, including
how to give insulin, monitoring your cat, and recognising and treating
hypoglycaemia.
Keys to management of diabetes in cats
(2011) is a presentation by Dr S Little to the 36th World Small
Animal Veterinary Association World Congress which compares the
various brands of insulin available and advises on how to adjust insulin
dosage.
