Blood (Serum) Glucose Test

What is the blood glucose test?

This test measures the amount of glucose (sugar) in your blood. Sugar is an important source of energy, especially for the brain. The amount of glucose in your blood is carefully controlled by the endocrine (glandular) system. This system causes sugar to be stored or used for energy, depending on the needs of your body.

A person can get glucose directly from some foods, such as table sugar. A person can also produce glucose when other foods, such as bread and cereal, are digested.

Why is this test done?

The most common use of the blood glucose test is to check for diabetes mellitus. The test is also used to see how well the body is metabolizing glucose and the function of organs involved in that process: the pancreas, the liver, and the receptors that bring glucose into cells.

How do I prepare for this test?

Your child usually does not need to fast or limit his or her activity before the first test.

If your child's first test is abnormal, a health care provider may ask your child to fast before repeating the test. The fasting test will show whether the abnormal result in the first test was caused by food your child ate before the test or some other reason.

The simplest way to check for diabetes is to check blood sugar (glucose) before anything is eaten in the morning. In most cases, your child will fast overnight, eating nothing and drinking nothing but water after an evening meal, and in the morning his or her blood is drawn.

Your child may need to avoid taking certain medicines before the test because they might affect the test result.

Talk to your child's health care provider if you have any questions.

How is the test done?

Your child's health care provider will poke a finger with a lancet and fill a small tube with the blood. Sometimes blood is taken from your child's arm through a needle instead of using a finger poke. The blood is collected and sent to a lab. Having this test will take just a few minutes.

How will I get the test result?

Ask your health care provider how you will get the result of your child's test.

What does the test result mean?

The normal fasting blood glucose range for children in most labs is 60 to 100 milligrams per deciliter (mg/dL). The normal range may vary slightly from lab to lab. Normal ranges are usually shown next to the results in the lab report. A fasting blood sugar level of 126 mg/dL or higher can mean your child has diabetes.

Blood glucose level may be higher than normal (called hyperglycemia) if:

• Your child has diabetes mellitus and:
  • diabetes medicines are not adequately controlling the condition
  • your child hasn't been following a diabetic diet.
• Your child has kidney or liver disease.
• Your child's pancreas is inflamed.
• Your child's body is severely stressed from a bad infection or injury.

Your child's blood glucose level may be lower than normal (called hypoglycemia) if:

• Your child is diabetic and:
  • the dose of insulin or other medicine used to control the diabetes is too high
  • your child took medicine for diabetes but then did not eat.
• Your child's thyroid, pituitary, or adrenal glands are not working normally.
• Your child has liver disease, problems absorbing food, or a diet low in needed nutrients.

What if my child's test result is not normal?

Test results are only one part of a larger picture that takes into account your child's medical history and current health. Sometimes a test needs to be repeated to check the first result. Talk to your health care provider about the result and ask questions.