What do the results of a blood glucose test mean?
Blood test reports, including blood glucose test reports, usually provide the following information:
- The name of the blood test or what was measured in your blood.
- The number or measurement of your blood test result.
- The normal measurement range for that test.
- Information that indicates if your result is normal or abnormal or high or low.
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What is a normal glucose level in a blood test?
A healthy (normal) fasting blood glucose level for someone without diabetes is 70 to 99 mg/dL (3.9 to 5.5 mmol/L). Values between 50 and 70 mg/dL (2.8 to 3.9 mmol/L) for people without diabetes can be “normal” too.
What does a high blood glucose level mean?
If your fasting blood glucose level is 100 to 125 mg/dL (5.6 to 6.9 mmol/L), it usually means you have prediabetes. People with prediabetes have up to a 50% chance of developing Type 2 diabetes over the next five to 10 years. But you can take steps to prevent Type 2 diabetes from developing.
If your fasting blood glucose level is 126 mg/dl (7.0 mmol/L) or higher on more than one testing occasion, it usually means you have diabetes.
In either of these cases, your provider will likely order a glycated hemoglobin test (A1c) before diagnosing you with prediabetes or diabetes. An A1c shows your average blood sugar over a few months.
There are a few different types of diabetes. The most common forms are:
- Type 2 diabetes (T2D): T2D happens when your pancreas doesn’t make enough insulin or your body doesn’t use insulin well (insulin resistance), resulting in high blood glucose levels. This is the most common type of diabetes.
- Type 1 diabetes (T1D): T1D is an autoimmune disease in which your immune system attacks the insulin-producing cells in your pancreas for unknown reasons. Your pancreas can no longer produce insulin. At diagnosis, people with Type 1 diabetes usually have very high blood glucose (200 mg/dL, or 11.1 mmol/L, or higher).
- Gestational diabetes: This condition can develop in pregnant people — usually appearing during the middle of pregnancy, between 24 and 28 weeks. The high blood sugar (diabetes) goes away once the pregnancy is over. Pregnant people have screenings for gestational diabetes with a glucose challenge test and/or glucose tolerance test.
Other causes of high glucose levels
Other causes of high glucose levels include:
- Issues with your adrenal glands, such as Cushing syndrome.
- Issues with your pancreas, such as pancreatitis.
- Hyperthyroidism.
- Experiencing significant stress, such as from surgery or trauma.
- Certain medications, especially corticosteroids.
What does a low blood glucose level mean?
A blood sugar result of 70 mg/dL or lower is usually considered low.
Low blood sugar (hypoglycemia) episodes are common in people with Type 1 diabetes and people with Type 2 diabetes who take certain medications. They’re much less common in people who don’t have diabetes.
If you don’t have diabetes, low blood glucose levels may be a sign of:
- Liver disease.
- Kidney disease.
- Hypothyroidism.
- Addison disease (adrenal insufficiency).
- Alcohol use disorder (AUD).
- Insulinoma (a rare tumor).
These conditions typically cause frequent low blood sugar episodes. A single low blood sugar test result usually isn’t a cause for concern in people who don’t have diabetes.
Should I be concerned if I have high or low blood glucose results?
If your glucose blood test result reveals that you have high or low levels of glucose, it doesn’t necessarily mean that you have a medical condition. Other factors, such as certain medications and not fasting, can affect your levels. There could’ve also been an error in the collection, transport or processing of the test.
Healthcare providers rely on more than a single blood glucose test to diagnose diabetes or another condition. In any case, your provider will carefully interpret your results and discuss them with you.
When should I know the results of a blood glucose test?
In most cases, you should have your venous blood glucose test results within 1 or 2 days.
Capillary blood glucose tests show the results within seconds via the glucometer.
When should I call my doctor?
If you’re experiencing concerning symptoms of low blood sugar or high blood sugar, contact your healthcare provider as soon as possible.
A note from Cleveland Clinic
Seeing an abnormal test result can be stressful. Know that having a high or low glucose level doesn’t necessarily mean you have a medical condition and need treatment. Approximately 1 in 20 healthy people will have results outside of the normal range. Your healthcare provider will let you know if you need to undergo further tests to determine the cause of the abnormal level. Don’t be afraid to ask your provider questions. They’re available to help you.
