Glucose, or blood sugar, is an important fuel for all parts of the body, including the brain. Cats that eat regularly can make enough glucose from their liver and from carbohydrates in the diet. Because glucose is so essential to life, it is important for pet parents to know what symptoms may indicate that your cat is experiencing glucose levels that are too high or too low.
Read on to better understand what could be causing changes in cat glucose levels and what pet parents can do about it.
What Is a Normal Cat Glucose Level?
Each individual cat will have a slightly different glucose level, and this fluctuates throughout the day. Glucose levels also fluctuate from day to day, so your cat will not have the same levels one day as the next.
Typically, all cats should have glucose values greater than 60 mg/dL. Any stress could increase blood glucose – even something as simple as having a visitor to your home. The high range of glucose readings for a healthy, low-stress cat would be around 160 mg/dL. However, cats that are stressed can increase glucose to 250 mg/dL. This is not technically abnormal unless it is always this high. Once cats reach a glucose level of 300 mg/dL, they will begin to show symptoms of having too much glucose.
No matter the size of your cat, the normal range of glucose in the bloodstream should be the same. In kittens under 4 weeks of age, having low glucose is much more dangerous and happens more often. This is because small kittens don’t have the same metabolism or reserves (not a lot of extra fat or places to store glucose).
Cat Glucose Level Chart
| Glucose Level | mg/dL |
| Low glucose (hypoglycemia) | <50 mg/dL |
| Normal glucose (normoglycemia) | 60-160 mg/dL |
| High glucose (hyperglycemia) / Stress suspected | 170-300 mg/dL |
| High glucose (hyperglycemia) / Diabetes suspected | > 300 mg/dL |
What Causes High Glucose Levels in Cats?
There are many causes of high glucose or hyperglycemia in cats. The most common is stress, which is a normal physiological response to any stress in life. Four other possible causes include:
Medicines. There are several medications, especially those used to induce anesthesia or sedatives, that will cause a spike in glucose. Steroids can cause an increase as well. Studies show that cats treated with very high doses of steroids for immunosuppression (1) are likely to develop a significant increase, whereas cats treated with lower anti-inflammatory doses do not (2).
Diabetes mellitus. The most common cause of persistent or chronic increase in glucose in cats, diabetes mellitus occurs either due to the lack of insulin in the body or the body no longer responds to insulin properly (known as insulin resistance).
After eating. All cats will experience a normal rise in glucose after eating. It is unusual for cats to have such an increase that the values exceed the normal. In one study (3), 17 percent of dogs had glucose levels higher than “normal range” after eating.
Pregnancy. Late in pregnancy, hormones change the body’s response to insulin. This will resolve in most cats very soon after birth.
Symptoms of high glucose levels in cats
Most cats will have temporary increases in glucose and no symptoms will be noted. Cats with prolonged relatively high glucose levels will show symptoms such as:
- Increased urine produced and increased thirst
- Increased appetite
- Reduced weight
- Less active
- Poor fur coat due to decreased grooming
- Enlarged (distended) belly
Treatment for High Glucose Levels in Cats
If the increase in glucose is due to the stress of an illness, such as an infection in the body, the treatment for high glucose addresses the underlying problem. However, cats with prolonged hyperglycemia can receive treatments such as:
A change in diet. Low carbohydrate, high protein diets are a staple in any cat experiencing chronic elevations in glucose. Dry food as well as canned diets that are thick have higher carbohydrates, so canned pate diets with particularly low carbohydrate levels are best.
Weight loss. Similar to humans, obese cats will have a better metabolism and their bodies will respond better to insulin if they lose weight.
Insulin. With a diagnosis of diabetes mellitus, cats are often prescribed insulin, an injection usually given twice daily to lower blood glucose levels.
Alternatives to insulin. It is possible to treat diabetes in cats without insulin. Otherwise healthy cats with diabetes not previously treated with insulin may be suitable candidates for an oral medication called Bexacat (bexagliflozin tablets). Given once a day, it blocks the kidneys from reabsorbing glucose so that the glucose can leave the body when a cat urinates.
What Causes Low Glucose Levels in Cats?
There are many causes of low glucose or hypoglycemia in cats. Causes may include:
Too much insulin given. If your cat is treated for diabetes mellitus with insulin injections, it is possible that the dose of insulin could cause the glucose to drop too low. If your cat takes Bexacatthere is minimal risk of low blood sugar, and there are no dose changes during treatment.
Liver disease. Any liver problem can lower glucose because the liver is the main place where glucose is made.
Sepsis. An infection that has invaded the bloodstream and spread throughout the body will make cats very sick, reducing their appetite and thus their glucose. Also, the body is fighting off a serious infection and will use up the glucose your cat has more quickly.
Poor nutrition. This happens more often in very young kittens. If a kitten is sick or does not have ready access to food, their glucose can drop very quickly. This is due to having a liver less able to produce more glucose and having less glucose stored in the body. Adult cats would have to experience starvation for a long time for this to happen.
Symptoms of Low Glucose Levels in Cats
Cats with a sudden drop in glucose instead of a chronic drop are more likely to show symptoms, such as:
- Lack of appetite
- Clumsy, stumbling or uncoordinated
- Weakness
- Change in consciousness and responses (mental state)
- Vomiting and/or diarrhea
- Seizures
Treatment for Low Glucose Levels in Cats
Treatment for low glucose involves supportive care and treatment of the underlying problem. Cats with symptoms of hypoglycemia are very sick and require urgent treatment from a veterinary hospital. Often, the vet will give an injection of dextrose to increase blood glucose immediately, then they will do various tests to determine an underlying cause. If you are treating your cat for diabetes mellitus with insulin injections, corn syrup or honey can be applied to your cat’s gums before taking them directly to the vet.
How to Check a Cat’s Blood Sugar
There are several ways to control blood glucose in cats. Blood glucose varies or changes slightly each day. If your cat is stressed while measuring the blood glucose, the reading will be significantly changed. Therefore, no method of measuring blood glucose is completely accurate. Your vet will focus on assessing blood glucose along with any symptoms of too much or too little glucose.
Methods for controlling blood glucose in cats may include:
Glucometer. Similar to people with diabetes, cats can check their blood glucose at home or at the veterinary hospital with a very small drop of blood. In cats, the most common place to get blood is the edge of the earlobe, or pinna.
Fructosamine. Fructosamine is basically an average of blood glucose levels over the previous 2-3 weeks. Your vet will send this test to a lab if your cat has had a high blood glucose reading and they are trying to determine if your cat has diabetes.
Glucose curve. When cats are being treated for diabetes mellitus, it is important to record what the blood glucose is at the highest and lowest points of the day. A glucose reading is taken every 1-2 hours. This can be done at home or at the veterinary hospital, but doing it at home is preferable to limit your cat’s stress.
Continuous glucose monitoring systems (CGMs). These devices are inserted under your cat’s skin and transmit the glucose measurement to a monitor outside the body.
How to Manage a Cat’s Glucose Levels
Pet parents can be proactive in ensuring the long-term health of their cats. To keep glucose in a normal range, maintain a healthy weight for your cat. If they start to gain weight, ask your vet how much you should feed your cat to maintain a healthy weight. Provide a quality cat food that is complete and balanced and limit treats, including human foods. As soon as your cat’s behavior or habits change, bring them to the vet. Treating any disease early will prevent your cat from developing severe changes in glucose.
References
- Lowe, AD et al. “Clinical, clinicopathological and histological changes observed in 14 cats treated with glucocorticoids.” The Veterinary record Vol. 162.24 (2008): 777–83. doi:10.1136/vr.162.24.777
- Khelik, Imal A et al. “Clinicopathological, hemodynamic, and echocardiographic effects of short-term oral administration of anti-inflammatory doses of prednisolone to systemically normal cats.” American Journal of Veterinary Research Vol. 80.8 (2019): 743-755. doi:10.2460/ajvr.80.8.743
- Yi, Katarina C et al. “Effect of withholding food versus feeding on creatinine, symmetrical dimethylarginine, cholesterol, triglycerides and other biochemical analyzes in 100 healthy dogs.” Journal of Veterinary Internal Medicine Vol. 37.2 (2023): 626-634. doi:10.1111/jvim.16630