Hyperglycemia is when there are higher levels of sugar in the blood than usual. Hyperglycemia is more common in teens and adults who have WS. Some teens and adults also have diabetes (a condition that affects how the body uses sugar for energy). Everyone has sugar in the blood to provide energy to the body.

Starting at puberty, it is important to check blood sugar regularly in people with WS. Blood sugar can be checked in 3 ways, all of which involve a blood test:

  • Fasting blood sugar (also called fasting glucose). This test checks the amount of sugar in the blood before someone has eaten for the day.
  • Oral glucose tolerance test. This test is also done before people have eaten for the day. The care team checks the amount of sugar in the blood. Then, your child drinks a beverage with a certain amount of sugar in it. Their sugar is tested again 2 hours later.
  • Hemoglobin A1c (HbA1c). This test can be done any time. It gives an average of what the sugar in your child’s blood has been over the past 3 months.


Most people with high blood sugar will not feel any differently. If blood sugar is very high, your child might have frequent urination, poor energy levels and increased tiredness.


People who have slightly high blood sugar should do their best to eat healthily and to be as active as possible. Walking and other exercises are great ways to lower blood sugar. People with Williams syndrome and diabetes also usually need to take a medication for diabetes. This can be a pill or insulin injections.

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Rev. 8/2019. Mass General for Children and Massachusetts General Hospital do not endorse any of the brands listed on this handout. This handout is intended to provide health information so that you can be better informed. It is not a substitute for medical advice and should not be used to treatment of any medical conditions.