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 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 tests 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.
Complete Blood Count
The table below shows some normal ranges for
different parts of the complete blood count (CBC). Some of the normal ranges
are different for 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
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 |
|---|---|
| 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.
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 |
Source: NHLBI, NIH