If I have diabetes and am sick, how often should I check my blood sugar?

Dr. Jack Merendino, MD

This depends on two things: what type of diabetes you have and how sick you are.

In general, people with type 1 diabetes need to check more often than those with type 2 diabetes anyway, but this is even more true when they are sick. People with type 1 diabetes are at risk for ketoacidosis, a serious or even life-threatening problem that results from there being very little insulin action. In ketoacidosis people have very high blood sugars and a build-up of certain acids in the bloodstream. People have flu-like symptoms with malaise, nausea and vomiting, abdominal discomfort muscle pain. As the condition becomes more severe, the individual may become difficult to arouse. If you have type 1 diabetes, you should also be doing urine testing for ketones when you are ill. This will detect ketoacidosis.

How often you test will also depend on how sick you are. With a mild cold, you may not need to test any more often than usual; with a severe infection you may need to test 3 or 4 times more often than usual.

As a general guide, for type 2 diabetes with a mild illness one should test twice daily and with a more serious illness 4 times per day or more if the numbers are fluctuating widely or rising rapidly. For type 1 diabetes, with a mild illness checking 4 to 6 times per day is a good ideas. If the illness is relatively severe, I usually tell my patients to test every couple hours, at least until it’s clear that the numbers are stable, and to do urine ketone testing. If the ketones are positive and the numbers are rising, it’s important to contact the healthcare provider.

If you have diabetes, sometimes you might not be feeling quite right and you don’t know why. Monitoring your blood glucose may tell you what the problem is. Maybe you’re feeling sweaty and a little shaky after a 3-mile run. Maybe you’re just tired from the workout, or maybe you’re having a low blood glucose reaction. Without monitoring, you may tend to eat because you think your blood glucose level is too low, when it is really too high. Only by monitoring your blood glucose can you tell what your body really needs.

No matter what kind of diabetes you have, measure your blood sugar and urine ketones more often than usual when you are sick. If you have type 1 diabetes, you may need to measure blood sugar and urine ketones every four hours. Measuring ketones is very important because these waste products are more likely to build up when you are sick and lead to ketoacidosis.

If you have type 2 diabetes, checking blood sugar four times a day may be enough. You might only need to measure ketones if your blood sugar is higher than 300. If you do not have a meter, talk to your diabetes educator about getting one.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.