10 Things Your Doctor Won’t Tell You About Your Blood Tests

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2. What’s considered “normal” differs between men and women

If you compare your blood test results with someone elses, you might be surprised to find differences. For example, the normal reference range for the number of red blood cells in a complete blood count, or CBC test, is between 5 million and 6 million cells per microliter for a man. The normal range is lower for women before menopause, between 4 million and 5 million, likely because of blood loss during menstruation.

3. Results can mean different things depending on your age

Normal levels of hemoglobin, part of the CBC test, vary by age — lower for children and higher for adults. For children, a hemoglobin level of 11 to 13 grams/deciliter (gm/dl) is normal, while for men, a value of 13.5 to 17.5 gm/dl is normal, and it’s 12 to 15.5 gm/dl  for adult women. Age matters for your cholesterol numbers, too. While most people should aim for LDL cholesterol levels below 130 milligrams/dl, levels of 160 to 190 mg/dl or above point to a risk for heart disease and are riskier if you are a man over 45 or a woman over 55, notes the Mayo Clinic.

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