Blood Testing

More on Blood Tests - Results

blood sample in a test tube A blood test shows whether the levels of different substances in your blood fall within a normal range.

For many blood substances, the normal range is the range of levels seen in 95 percent of healthy people in a certain group. For many tests, normal ranges are different depending on your age, gender, race, and other factors.

Many factors can cause your blood test levels to fall outside the normal range. Abnormal levels may be a sign of a disorder or disease. Other factors-such as diet, menstrual cycle, how much physical activity you do, how much alcohol you drink, and the medicines you take (both prescription and over-the-counter)-also can cause abnormal levels.

Your doctor should discuss any unusual or abnormal blood test results with you. These results may or may not suggest a health problem.

Blood test results alone can't be used to diagnose many diseases or medical problems. However, blood tests can help you and your doctor learn more about your health. Blood tests also can help find potential problems early, when treatments or lifestyle changes may work best.

Result Ranges for Common Blood Tests This section presents the result ranges for some of the most common blood tests.

NOTE: All values in this section are for adults only. They don't apply to children. Talk to your child's doctor about values on blood tests for children.

Blood Glucose

This table shows the ranges for blood glucose test results after 8 to 12 hours of fasting (not eating). It shows the normal range and the abnormal ranges that are a sign of prediabetes or diabetes.
Plasma Glucose Results (mg/dL)*Diagnosis
99 and below Normal
100 to 125 Prediabetes
126 and above Diabetes+

* mg/dL = milligrams per deciliter.
+ The test is repeated on another day to confirm the results.