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Monitoring |
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Introduction | Blood Glucose | Urine Glucose | Drinking | Fructosamine | Water/Dry Matter Ratio
Introduction
Monitoring is a critical element in managing a diabetic cat. With the importance of getting the balance right in the amount and type of insulin and in the timing of the injections, monitoring provides the reassurance and confirmation that all is OK as well as a warning when things start to go wrong.
There are several ways to monitor a cat's diabetes and most owners caring for a diabetic cat use more than one. Each method has its own advantages and disadvantages, so there are no right or wrong approaches. I once read somewhere that the most important thing is to make sure that you are using methods with which you are comfortable and that your cat accepts. They have to be right for your cat and for you. Otherwise it is likely that the quality of care may decrease over time. This is something which, with the benefit of several years experience, I firmly believe. Close contact and co-operation with the vet is also important.
This almost seems like stating the obvious, but a key part of caring for a diabetic cat is to look for any changes, whether they might be subtle or major. The changes can be in behaviour, activity, feeding, drinking, demeanour, in fact just about anything. If any changes are noticed, it might be necessary for a visit to the vet to assess whether they are related to the diabetes.
Home Blood Glucose Monitoring
This is the most accurate method of monitoring a cat's diabetes because it gives an up to date snapshot of the cat's blood glucose (BG) level at that moment in time. However it is not suitable for all diabetic cats or their owners and many diabetic cats are successfully stabilised without using this method at all. This includes Susie.
The method is based on taking a small amount of blood, usually a pinprick from the ear in cats (the lip or paw are more commonly used in dogs) and measuring the glucose level with a special meter, the same sort that is popular for measuring BG in people with diabetes.
It is particularly useful if the cat's BG curve has previously been measured after being stabilised. A BG curve is a graph showing the change in BG over a 12 or 24 hour period. It is normally measured at a veterinary surgery or animal hospital and it should take account of the normal insulin dosage. It helps to demonstrate that the dosage and type of insulin is controlling the BG levels effectively.
A cat's blood glucose will naturally vary throughout the day, being influenced by factors such as eating and activity, so it is important to match up the snapshot figure correctly to the graph.
Two advantages of this method are:
- Adjusting the insulin dosage: if the BG is unusually high or low compared to the graph, the insulin dose can be adjusted accordingly. Any change in insulin dosage should be small and it is generally better to discuss this with the vet first. This allows the BG to be kept close to the ideal range without going too low which would risk hypoglycaemia, or too high resulting in glucose spilling over into the urine.
- Unexpected results: dangerously low or high BGs can be highlighted quickly and appropriate advice or urgent treatment sought in good time.
This method appears to be more commonly used in the USA and Canada than in the UK. Some anecdotal comments:
- When I first discussed this with my previous vets, they were unaware of it and strongly discouraged me from considering it.
- I have heard the view expressed that it is more beneficial measuring it in larger dogs than in cats.
- When changing to my current vets in 2000, none of the practices or veterinary hospitals that I contacted had any experience of this method in any animals.
- One opinion offered by my previous vet was that home BG testing might cause more stress and that quality of life should also be considered.
- A locum vet at my current practice told me of one case in which the bond between the animal and its owner had been broken by a lot of home testing for a different condition.
Urine Glucose Monitoring
This is a much simpler procedure and is far less invasive than BG testing (above), but it has more limitations. This was the main method that I used for Susie since she became diabetic in 1999.
A test stick is dipped into the urine. I use Keto-Diastix® (Bayer) which have 2 small strips, one for ketones, the other for glucose. Different people have found a range of ways of obtaining samples. Over the years, I have tried several different approaches, but by far the easiest is this:
- I would have the pot of test sticks close to Susie's litter tray.
- while she was using the tray, I would get one of the sticks ready and a small piece of tissue.
- as soon as she had finished, I would dip the stick into the wet litter and wipe it with the tissue.
- after 30 seconds (it is important to time this accurately), I would check the colour of the test strip against the chart on the side of the pot to read off her urine glucose level - see illustration below.
Elsewhere, I have read that it is better to try to use some non-absorbent material in the litter tray such as fishtank grit when trying to obtain a sample. Having tried this, my experience is that it was messy and cumbersome, difficult to clear up, and not worth the effort. In addition, Susie didn't like using it. I found that Susie's usual litter tray material, fuller's earth, worked perfectly well, provided that I was quick enough with the test stick, dipping it into the wet litter as soon as she stepped away.
The main limitations of urine glucose testing are as follows:
- Glucose will only be found in the urine if the glucose level in the blood had become high enough for the kidneys to begin to filtering it out of the blood. If, since the cat last urinated, the BG level had never reached this point, the urine glucose figure will be negative.
- It only represents an average figure for the time since the cat last urinated. This can hide the highs and lows in BG level, so it can be dangerous to rely on this alone. This point is particularly important when the cat is close to being stabilised, because the insulin dosage will be higher and the period between urinating longer.
- This method can therefore not detect low BG levels.
- It is important if using this as the main method to keep a close check on the cat's behaviour to watch for any signs of hypoglycaemia. Twitching, trembling and unusual lethargy are examples of key early indicators. The period of greatest risk is when the insulin is at the peak of its activity.
For these reasons, if relying on urine glucose monitoring, the aim is to have readings that are slightly positive rather than zero. This minimises the risk of hypoglycaemia. My previous vet recommended that if I got a negative reading, I should decrease Susie's insulin dosage very slightly for 3-4 days. In practice, I would reduce Susie's insulin dosage if I got 2-3 consecutive zero readings and I wouldn't increase it unless her urine glucose was 1% or more for at least 2-3 consecutive readings.
Drinking
If diabetes is poorly controlled, the BG level will be very high. This makes the kidneys work hard at removing the excess sugar. As the sugar is taken out by the kidneys, a lot of water goes with it. The lost water needs replacing and this produces thirst and the need to drink.
When diabetes is either uncontrolled or partially controlled, the amount of fluids drunk will be higher than normal, so any changes in drinking patterns should be noted. There are all sorts of ways of recording this information. I used the following approach:
- I would have 2 bowls of water available for Susie in different locations which I replaced twice daily.
- Each time I put a new water bowl out, I would weigh it with the fresh water in ("initial").
- When I next changed the bowls, I would weigh the old ones again, with the unused water still inside ("final").
- The difference between the initial and final figures was the amount of water that Susie had drunk.
It is also important to take into account any other water sources. For example, some cats like to find dripping taps in basins or baths, or to find a puddle of rainwater outside. This is difficult to quantify, but making a note of it might help to explain an unusually high or low figure.
Other conditions can also have an effect on water intake, notably kidney disease and hyperthyroidism, so these also need to be considered.
Fructosamine and Glycosylated Haemoglobin
Blood glucose and urine glucose are extremely valuable indicators of diabetes, but on their own they have limitations:
- Blood Glucose (whether measured at home or by the vet) provides a snapshot of the blood glucose level at that particular moment
- Urine Glucose provides an indication of whether the blood glucose level over the last few hours (since the cat last urinated) became high enough for the kidneys to start removing the excess from the blood (the renal threshold)
Taken in isolation, a single high result for either of these could be the result of other causes. Since diabetes is characterised by persistent high blood glucose over a period of time, a measurement is needed that indicates high blood glucose over a much longer period. This is where fructosamine and glycosylated haemoglobin (sometimes known as glyco-haemoglobin) are useful.
Fructosamine is sometimes called "serum fructosamine". This simply means that the measurement is taken on the liquid carrier part of the blood known as the serum (i.e. after the blood cells have been separated out).
They both give an indication of the average blood glucose level over the last few weeks, and therefore an indication of how well the diabetes is being controlled. They can also be used to assist in the initial diagnosis of diabetes.
Fructosamine and glycosylated haemoglobin concentrations are normally higher in diabetic cats than in non-diabetic cats. Furthermore, if the cat's diabetes is well controlled, the levels might only be slightly increased (or even occasionally within the normal range), whereas for poorly regulated diabetes the levels would be significantly higher.
Fructosamine figures give an indication of the blood glucose level over about the last 2 weeks (different sources indicate times between 1-3 weeks). Glycosylated haemoglobin figures are slightly longer term, typically about 1-2 months in cats, but again different sources indicate slightly different durations. The tests are carried out from a sample taken at the veterinary surgery or hospital. Results are compared with reference values for that laboratory, since different labs use slightly different methods or equipment. Units can also vary. It is worth bearing these points in mind, because there are various examples of typical figures available on the internet.
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Example - Susie's Fructosamine Figures The reference ("normal") levels for the lab that has done most of Susie's tests are 221-341 µmol/L. My vet advised that in uncontrolled diabetes the level would be typically around 750 µmol/L. For intermediate levels, the following figures are used as a guide by the lab for cats on therapy for diabetes mellitus:
These tests provide another useful indicator of diabetes control, but the results should always be taken in the context of the full picture, including observations of the cat's behaviour and health and any recent urine or blood glucose results. It is important to be aware of the reference values for whichever lab is being used, because they help to place the figures in context. The results for different labs cannot be compared directly with each other if their reference values are different. To illustrate this, I have shown the results of all of Susie's fructosamine tests. Up to April 2004, all of the tests were carried out at the same lab, with reference values as indicated above (221-341). In September 2004, the vets started using a different lab with lower reference values (146-271). Susie's figure of 348 would have been in the "excellent control" range at the old lab, but I suspect that it was merely "good" or even "fair". After discussing my concerns with my vet, I was able to return to the original lab from Jan 2005.
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Finally, for interest only, a bit abut the chemistry:
The principle of both measurements is: Of the glucose present in the blood, a small proportion of it binds to other blood components. The new compounds that are formed from this binding remain in the blood for several weeks and their concentrations can be measured. Normally they would be very low but if the blood glucose level has been persistently high, their levels are increased. Short term increases in blood glucose do not last for long enough to have any effect on these figures, so they are able to differentiate between stress hyperglycaemia (short lived) and diabetes (persistent).
- Fructosamine - the products that result from glucose in the blood binding to various proteins in the blood serum (the liquid part that carries the blood cells). A more scientific definition is: a general term given to all glycated serum compounds that result from the binding of blood sugar to the amino group of any serum protein. The term "fructosamine" is therefore not a single chemical entity.
- Glycosylated Haemoglobin - the product that results from glucose in the blood binding to part of the red pigment inside the red blood cells (to a specific haemoglobin fraction).
Water to Dry Matter Ratio
This ratio is one that I found to be extremely valuable when monitoring Susie's progress towards stabilisation. Although I have found comments on other websites about the amount of water being reduced as the condition is stabilised, which I have also observed with Susie, I am not aware of anybody else measuring this ratio.
In principle, it simply takes into account all of the other food-related factors that can affect the water intake. These include the amount of food eaten and the water content of the food, which can vary enormously. By correcting for variations in these, it should in theory provide a truer indication of the variation in water intake due to diabetes control.
Its main benefit is in looking at trends over a period of time, but I have also found it to respond significantly to a single missed injection and to periods of reduced insulin dosages. It is not a substitute for very short term measurements or observations such as blood glucose measurements or signs of hypoglycaemia, but it can be useful as part of a series of monitoring techniques.
I found this measurement to be very valuable when things were less stable or more variable - before Susie's diabetes was properly controlled and in periods when she had been on a mixed or moist-food diet. In more stable situations and when on an exclusively dry food diet, measuring the amount of water that she drinks was perfectly adequate.
For more details, see the Ratio page.
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