Harvard Health Letter

What is normal?

The shifting boundaries of normal and healthy cholesterol levels, blood pressure, and other health indicators.

It seems that the definitions of normal, healthy levels of blood pressure, cholesterol, and other health indicators keep changing, so that increasing numbers of people are classified as being at risk and therefore in need of treatment. Yesterday's normal becomes today's needs-to-be-treated.

More than a few people have wondered why the bar keeps moving, and whether standards change just so doctors, laboratories, and other health care providers can generate more business for themselves. Doctors and others in health care aren't immune to the pursuit of self-interest, but there's a better, fuller explanation for the migrations of normal.

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