A high blood sugar level in a cat may or may not be caused by a medical condition. We need to assess the severity of the blood sugar rise and determine if it may be medically significant. For many of the cats I see in my clinic, they will have a blood sugar rise due to the stress of being in the vets, rather than any medical condition.
When high glucose levels are caused by a medical issue in cats, diabetes would be the most common one we see. However, these cats will have other symptoms. Certainly, an elevation in blood sugar is something that we should always take a closer look at.
Overview of high blood sugar in cats: how does it impact my cat?
Firstly, we need to be cautious when jumping to conclusions. A mild increase in blood sugar levels in an otherwise well cat, is probably just a stress response. These cats won’t have any signs of persistently elevated blood sugar and should not have glucose in their urine.
When high sugar levels are caused by a medical issue such as diabetes, this will have a profound effect on our cats and their quality of life.
Severity of high blood sugar in cats (with chart) (1)
Sugar level Comment Treatments
80-120mg/dl Normal None
120-400mg/dl High May or may not be needed
>400mg/dl Very high Treatment for diabetes may be required
What are the causes of high blood sugar in cats?
When a cat is very stressed, for example, after being transported to the vets or when being handled for a blood sample, temporary glucose spikes are not uncommon. They occur alongside spikes in adrenaline and lactate (2). It is likely that the lactate released triggers new sugar to be formed and released into the blood, in readiness for a fight or flight response. For most cats, glucose levels return to normal within 90 minutes.
Signs of stress can include tail wagging, hiding away, trying to run away and ‘freezing’. Some cats also purr as they try to self-soothe. It is not always easy to spot when a cat is stressed and signs can be subtle.
A recent high calorie meal
It is no surprise that eating will cause sugars to be circulating in the blood. If a cat eats prior to a blood test, levels can rise as high as 300mg/dl. This is why we need to take a fasted blood sample when measuring blood glucose levels. When sugar spikes are mild and temporary, there is no need for treatment as this is a normal physiological response. The cat will have normal Fructosamine levels (a blood test to measure the average blood levels over the previous few weeks) and should not have glucose in their urine.
When we think of high blood sugar levels, diabetes is often what springs to mind. This is a common endocrine disorder, with up to 1 in 100 cats developing it during their lifetime (3). Signs can include excess thirst and urination, excess hunger and weight loss. Diabetes can make cats very unwell and, if left untreated can progress to a life-threatening conditions known as ‘ketoacidosis’. For this reason, we want to try and manage diabetes as soon as it is diagnosed. This will usually include a diet change, treatment of any concurrent infections and ongoing insulin injections. For some cats, their diabetes is reversible with interventions including weight loss and diet change.
When the pancreas is inflamed, it cannot produce insulin as it should, so the glucose remains circulating in the blood. Cats with pancreatitis will be clearly unwell and will show signs including food refusal, lethargy, abdominal pain and vomiting.
Cats typically require hospitalisation for treatment with a fluid drip and injectable medicine including pain medicine. Pancreatitis can sometimes be prevented by avoiding high fat foods.
Infections can drive blood sugar levels temporarily high. For this reason, it is always sensible to conduct a full physical exam on the patient, checking for any underlying issues such as an oral abscess or anal gland disease. A urine analysis should also be run, to check for a urinary infection. Once the infection has been treated (which usually requires a course of antibiotics), the blood sugar levels will return to normal.
What are the symptoms and signs of high blood sugar in cats?
When a blood sugar rise is temporary (like after a period of stress, excitement or eating) there won’t be any symptoms. However, pathological causes of high blood sugar will cause symptoms including:
- Excess thirst; a cat drinking more than 100mls/kg/day.
- Excess hunger. Some owners mistakenly believe that this is a ‘good’ sign, but it is simply that the cat’s body does not recognise it has been fed.
- Weight loss. We may notice the cat looks skinnier over their spine and back legs.
- Walking in a plantigrade stance – see picture (the weight is on the back ankles, rather than the paws). This is an uncommon sign which is not painful for the cat and should reverse once their sugar levels are controlled.
Treatment options for cats with high blood sugar
Whether or not the cat will need treatment depends on why their blood sugar levels are high. Certainly, cats who are diagnosed with a medical disorder such as diabetes, an infection or pancreatitis will require urgent veterinary treatment.
Thankfully, high blood sugar is generally something that we can manage well and, for most cats, we can get their sugar levels back to within normal limits.
When a cat has diabetes, they may need lifelong insulin and a low carbohydrate diet. However, some cats will go into remission, meaning their insulin treatment can be stopped.
When to consult the vet
Any signs of chronic high blood sugar, such as weight loss or an excessive thirst, would warrant a vet visit.
Checking for high sugar levels is very straightforward, and a blood and urine sample can be taken within a matter of minutes in a routine consultation.
Frequently Asked Questions
How can I monitor my cat’s blood sugar levels at home?
Some owners of diabetic cats will have blood glucose meters that they use from home, to monitor their cat’s levels regularly. It can also be useful to use urine dipsticks, to check for sugar or ketones in the urine. More often, it is the vet who monitors the patient’s blood sugar levels, within the clinic.
Can diet alone control high blood sugar in cats?
Some diabetic cats respond very well to a restricted carbohydrate diet and weight loss plan, and this can lead to a normalisation of their blood sugar levels.
What are the potential complications if high blood sugar is left untreated?
Not treating high blood sugar is extremely risky. Cats can develop ketoacidosis, whereby fat is converted into ketone bodies as the body is unable to use the sugar that is circulating. This process is dangerous, and it disturbs both the salt and the acid-base balance within the cat’s body. Having high sugar levels long-term also makes a cat more prone to infections. liver problems, nerve damage and muscle wastage.
Are there any specific cat breeds that are more prone to diabetes?
We know that certain purebred cats, including the Siamese and Burmese, are more prone to diabetes. However, it can afflict any breed including cross-breeds and Domestic Short Hairs/Long Hairs.