Cat Glucose Levels: What’s Normal?

Glucose, or blood sugar, is an important fuel for all parts of the body, including the brain. Cats who regularly eat can make enough glucose from their liver and from carbohydrates in the diet. Since glucose is so vital to life, it is important that pet parents know what symptoms may indicate your cat is experiencing glucose levels that are too high or too low. 

Read on to better understand what might cause 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 they will the next.

Typically, all cats should have glucose readings over 60 mg/dL. Any kind of stress could increase glucose in the blood — even something as simple as having a visitor over to your home. The high end of glucose readings for a healthy, low-stress cat would be around 160 mg/dL. However, cats who 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 of 300 mg/dL, they will start 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 frequently. This is because small kittens do not have the same metabolism or reserves (not a lot of extra fat or places to store glucose).

Cat Glucose Levels 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 multiple causes of high glucose or hyperglycemia in cats. The most common is stress, which is a normal physiologic response to any stress in life. Four other possible causes include:

Medications. There are several medications, especially ones used to induce anesthesia or to sedate, that will cause a spike in glucose. Steroids may 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 increase in glucose after eating. It is uncommon for cats to have such an increase that the values go above normal. In one study (3), 17 percent of dogs had glucose 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 giving 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
• Decreased 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 stress of disease, such as an infection in the body, the treatment for high glucose is treating the underlying issue. However, cats with prolonged hyperglycemia may receive treatments such as:

Change in diet. Low carbohydrate and high protein diets are a staple in any cat experiencing chronic increases in glucose. Dry food as well as canned diets that are chunky 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 better respond to insulin if they lose weight.

Insulin. With a diagnosis of diabetes mellitus, cats are often prescribed insulin, an injection typically given twice daily to decrease levels of glucose in the blood.

Insulin alternatives. 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 daily, 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 multiple causes of low glucose or hypoglycemia in cats. Causes may include:

Too much insulin given. If your cat is being treated for diabetes mellitus with insulin injections, it is possible that the insulin dose could cause glucose to decrease too much. If your cat is taking Bexacat, there is minimal risk of low blood sugar, and there are no dosage changes during treatment.

Liver disease. Any kind of liver issue can decrease glucose because the liver is the primary place where glucose is made.

Sepsis. An infection that has invaded the bloodstream and spread throughout the body will make cats very ill, 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 occurs more often in very young kittens. If a kitten is sick or does not have ready access to food, their glucose can very quickly decrease. This is due to having a liver that is less capable of making more glucose and having less glucose stored in the body. Adult cats would need to experience starvation over a long period of time for this to happen.

Symptoms of Low Glucose Levels in Cats

Cats with sudden decreases in glucose instead of chronic decreases are more likely to show symptoms, such as:

• Lack of appetite
• Clumsy, stumbling, or uncoordinated
• Weakness
• Change in awareness and responses (mental status)
• Vomiting and/or diarrhea
• Seizures

Treatment for Low Glucose Levels in Cats

Treatment for low glucose involves supportive care and treating the underlying issue. Cats with symptoms of hypoglycemia are very sick and require emergency treatment by a veterinary hospital. Oftentimes, the veterinarian will give an injection of dextrose to increase blood glucose right away, then they will run a variety of 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 prior to bringing them straight to a veterinarian.

How to Check a Cat’s Blood Sugar

There are multiple ways to check blood glucose in cats. Blood glucose fluctuates or changes somewhat day to day. If your cat is stressed while measuring the blood glucose, the reading will be significantly changed. Therefore, no method of blood glucose measurement is perfectly accurate. Your veterinarian will focus on evaluating blood glucose along with any symptoms of having too much or too little glucose.

Methods of checking blood glucose in cats may include:

Glucometer. Similar to humans with diabetes, cats can have their blood glucose checked at home or in the veterinary hospital with a very tiny drop of blood. In cats, the most common place to get blood is the edge of the ear flap, or pinna.

Fructosamine. Fructosamine is essentially an average of levels of blood glucose over the previous 2-3 weeks. Your veterinarian will send this test to a laboratory if your cat had a high blood glucose reading and they are trying to decide if your cat has diabetes mellitus.

Glucose curve. When cats are treated for diabetes mellitus, it is important to record what the blood glucose is at the highest and lowest points of the day. Glucose readings are taken every 1-2 hours. This can be done at home or at the veterinary hospital, but doing it at home is preferred to limit your cat’s stress.

Continuous glucose monitoring systems (CGMs). These pieces of equipment are inserted under your cat’s skin and transmit the glucose measurement to a monitor outside of 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 levels in a normal range, maintain a healthy weight for your cat. If they begin gaining weight, ask your veterinarian how much you should feed your cat to maintain a healthy weight. Provide quality cat food that is complete and balanced and limit treats, including human food. As soon as your cat’s behavior or habits change, bring them to the veterinarian. Treating any illness early on will keep your cat from developing severe changes in glucose.

References

1. Lowe, A D 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
2. Khelik, Imal A et al. “Clinicopathologic, 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
3. Yi, Katarina C et al. “Effect of withholding food versus feeding on creatinine, symmetric dimethylarginine, cholesterol, triglycerides, and other biochemical analytes in 100 healthy dogs.” Journal of veterinary internal medicine vol. 37,2 (2023): 626-634. doi:10.1111/jvim.16630