Hyperglycemia, or high blood glucose, occurs when there is too much sugar in the blood and not enough insulin. When your insulin level is low, your body is unable to use the glucose. The glucose then gets too high and your body breaks down its own fat for energy instead of glucose. When fat is used for energy, your body releases fat into the blood to be used for fuel. If there is too much fat, the liver produces substances called ketones.  Ketones are the waste products of fat burning. In the absence of insulin, ketoacids are also produced. Ketoacids can be toxic when they build up in the blood.

Ketones appear in the urine and can be measured using special test equipment. For a person with type 1 diabetes a blood glucose level more than 300 mg/dl may indicate there is not enough insulin, and there is a risk of building up ketones. Too many ketones in your blood can cause an emergency condition called ketoacidosis.

How do I test for ketones?
Testing for ketones is done by dipping a test strip into your urine. The test strip changes color and is then compared to a color chart.

When should I test for ketones?
If you have type 1 diabetes, test your urine for ketones when:

• Your blood glucose is over 300 mg/dl
• You feel sick (have a cold, the flu or other illness) and have nausea or vomiting

If you have type 2 diabetes, you have a very low chance of developing ketoacidosis, even if you are on insulin therapy. However, during severe illnesses, it is possible that ketoacidosis may develop. You should test your urine for ketones when:

• You feel severely sick (have a cold, the flu or other illness) and/or have unexplained nausea or vomiting
• Your blood glucose level is high (> 300 mg/dl) and continuing to rise throughout the day. most of the time

When should I call my doctor?
The result of your urine test for ketones should always be negative. Any positive results should be reported to your doctor immediately. You should also call your doctor right away if your blood glucose remains elevated or if you have stomach pain, nausea, vomiting, rapid breathing or sweet-smelling breath.

How do I record my test results?
Keep good records of any urine or ketone tests you do. Your records can help alert you to any problems. Also, these test records help your doctor make any needed changes in your meal plan, medication or exercise program. Bring these records with you every time you visit your doctor.

© Copyright 1995-2007 The Cleveland Clinic Foundation. All rights reserved