Susie, Diabetic Cat
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What is Diabetes?

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The Basics | Types 1 and 2 | Symptoms | Blood Glucose Units

The Basics

First of all, I need to point out that my experience is from managing a diabetic cat and trying to find out everything that I could about the condition.  All content that you might read on these pages is published in this context.

Let's start with the basics.  Sugar is one of the components of food and is needed for energy.  When we eat, the sugar in the food is absorbed into the bloodstream where it is known as "blood sugar".  It is distributed all around the body in the blood and is passed into the cells where it is used up as a source of energy.  When the sugar is passed from the blood into the cells, it needs a special chemical to help it.  This chemical is called insulin.

Insulin is produced within the body by special cells in the pancreas and diabetes (more correctly called diabetes mellitus or sugar diabetes) is a condition in which the body does not produce enough insulin, sometimes producing none at all.  Without insulin, the sugar cannot pass into the cells.  Instead it remains in the blood and, as it builds up, is eventually removed by the kidneys, spilling over into the urine.

To add a little more detail to this, a certain amount of sugar in the blood is therefore normal, and is actually essential, because the body's cells need a constant source of energy.  In diabetes, because the sugar can't get from the blood into the cells, it starts to build up in the blood, eventually reaching a level where it triggers a response from the kidneys.  The job of the kidneys is to filter out waste products from the blood.  When the sugar level builds up to a certain level (known as the renal threshold), the kidneys get to work and start removing it.  In the process, a lot of water is also filtered out with the sugar.  This water has to be replaced which is what produces the thirst, a common symptom.  The waste sugar and the accompanying water are passed into the urine and out of the body.  

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Types 1 and 2 Diabetes

Most sources refer to 2 types of diabetes.  They are very similar to the 2 types seen in humans:

Type 1 Diabetes:
Little or no insulin is produced by the body.  This type of diabetes often develops at an early age, just as it does in humans.  It always has to be treated with insulin injections, and is therefore sometimes referred to as "insulin dependent diabetes mellitus" or IDDM.

Type 2 Diabetes:
This is the more common type in cats, although I have seen widely differing figures on how common it really is.  It has a range of causes and it usually occurs later in life.  A major risk factor is obesity and in such circumstances weight loss can help to reduce the symptoms or even remove them altogether.  This type of diabetes might also respond to other types of medication, although insulin is still widely used together with dietary control.  Because it can sometimes be treated without insulin, Type 2 diabetes is sometimes referred to as "non insulin dependent diabetes mellitus" or NIDDM.

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Symptoms

There are 4 key symptoms which can be used as an initial indicator of diabetes.  Diagnosis is often made difficult because the 4 main signs can also be present in other conditions.  Most diabetic cats will not exhibit all of them, but any 2 or 3 seen together will normally suggest diabetes.  Diagnosis is confirmed by further tests.  The 4 key symptoms are:

increased hunger:   the body thinks that it is short of food because the sugar (glucose) cannot get into the cells
increased urination: the excess glucose in the blood that cannot get into the cells is expelled into the urine by the kidneys
increased thirst: as the glucose is expelled by the kidneys, it takes a large quantity of water with it, which has to be rapidly replaced to avoid dehydration
weight loss: because the body is unable to use sugars, it begins to use other energy sources, i.e. carbohydrate and fat reserves and proteins

One of the first things that the vet will do is take a blood sample to measure how much sugar is in the blood (the blood glucose or BG level).  Even this on its own can unreliable because many cats do not like travelling and the stress of the journey can lead to significant temporary increases in BG, hiding the real figure.  Cats, much more than dogs, have a very strong stress response, and going to the vets and having a blood sample taken can be very stressful!

Diagnosis is confirmed by persistent high BG, particularly after fasting.  Similarly, persistent glucose in the urine is a diagnostic indicator.

Although every cat is different, in the case of my cat Susie the first symptom that I noticed was her sudden dramatic increasing thirst.  In a matter of days, her drinking habits changed from barely touching the water in her drinks bowl to completely emptying 2 bowls in each 12 hour period.  It was only afterwards that I realised she had been using the litter tray more frequently for a number of weeks before I noticed the change in her drinking patterns.

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Blood Glucose Units

Since measuring the amount of glucose in the blood (and in the urine) is the key to managing diabetes effectively, it is important to be aware that two different units are used in different parts of the world.  Of course it would be more convenient if only 1 unit was used, but this is not the case.

One unit is used in most countries (Europe, Australia, Canada and much of the world) and another in the USA.

This is relevant because even today the majority of websites are based in the USA and some quote figures only in American units.  A few sites that I have seen don't even bother to specify which units they are using, leaving the reader to guess.  Fortunately, an increasing number of sites are well written and recognise the global nature of the internet by quoting figures in both units.

Unit Where Used What it Means
mmol/L Most countries millimoles per litre.  Multiply this figure by 18 to convert it to mg/dL.
mg/dL USA milligrams per decilitre.  Divide this figure by 18 to convert it to mmol/L.

Throughout the pages on this site, I have tried to quote both figures and I always include the units after the figures to avoid any misunderstanding or confusion.  For illustration, a typical BG figure might be 100 mg/dL (USA) or 5.6 mmol/L (international).

Why the conversion factor of 18?
Whilst this is only background information and is not important, it might be of interest if you have a bit of an understanding of chemistry.

  • The chemical formula of glucose is C6H12O6 so it has a molecular weight of 180
  • 1 mmol of glucose therefore weighs 180 mg, or to express it in units of concentration, 1 mmol/L = 180 mg/L.
  • A decilitre (dL) is 0.1 litres (L), so 1 mmol/L = 180 mg/L = 18 mg/dL.
  • i.e. the conversion factor is 18.

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Important note:  All information and opinion in the Susie, Diabetic Cat pages is from personal experience.  Nothing in these pages is intended to be a substitute for proper professional advice, which should always be sought from a qualified veterinary surgeon.

This page was last updated
May 2006