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What Do Blood Tests Show?

Blood tests show 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 vary depending on your age, gender, race, and other factors.

Your blood test results may fall outside the normal range for many reasons. Abnormal results might be a sign of a disorder or disease. Other factors—such as diet, menstrual cycle, physical activity level, alcohol intake, and medicines (both prescription and over the counter)—also can cause abnormal results.

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

Many diseases and medical problems can't be diagnosed with blood tests alone. 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.

Complete Blood Count

The table below shows some normal ranges for different parts of the complete blood count (CBC) test. Some of the normal ranges differ between men and women. Other factors, such as age and race, also may affect normal ranges.

Your doctor should discuss your results with you. He or she will advise you further if your results are outside the normal range for your group.

Test Normal Range Results*
Red blood cell (varies with altitude) Male: 5 to 6 million cells/mcL

Female: 4 to 5 million cells/mcL
White blood cell 4,500 to 10,000 cells/mcL
Platelets 140,000 to 450,000 cells/mcL
Hemoglobin (varies with altitude) Male: 14 to 17 gm/dL

Female: 12 to 15 gm/dL
Hematocrit (varies with altitude) Male: 41% to 50%

Female: 36% to 44%
Mean corpuscular volume 80 to 95 femtoliter

* Cells/mcL = cells per microliter; gm/dL = grams per deciliter.
A femtoliter is a measure of volume.

Blood Glucose

This table shows the ranges for blood glucose levels 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
70 to 99 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.

Lipoprotein Panel

The table below shows ranges for total cholesterol, LDL ("bad") cholesterol, and HDL ("good") cholesterol levels after 9 to 12 hours of fasting. High blood cholesterol is a risk factor for coronary heart disease.

Your doctor should discuss your results with you. He or she will advise you further if your results are outside the desirable range.

Total Cholesterol Level Total Cholesterol Category
Less than 200 mg/dL Desirable
200–239 mg/dL Borderline high
240 mg/dL and above High

LDL Cholesterol Level LDL Cholesterol Category
Less than 100 mg/dL Optimal
100–129 mg/dL Near optimal/above optimal
130–159 mg/dL Borderline high
160–189 mg/dL High
190 mg/dL and above Very high

HDL Cholesterol Level HDL Cholesterol Category
Less than 40 mg/dL A major risk factor for heart disease
40–59 mg/dL The higher, the better
60 mg/dL and above Considered protective against heart disease

 

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January 6, 2012