How Is Osteoporosis Diagnosed? A Doctor Explains

These tests are the only way to reveal bone health before fracture occurs.

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You might associate certain symptoms with osteoporosis, like frailness or a stooped posture, but the truth is, those characteristics don’t develop until osteoporosis has reached an advanced stage. In the earlier stages of osteoporosis, the disease is much more silent.

“The only way to know if you have osteoporosis is by doing a bone density test,” says Sonal Chaudhry, MD, endocrinologist at NYU Langone Health. There’s one exception: “If you’ve had a fragility fracture in the past, that by definition means that you do have osteoporosis.”

Bone Density Tests for Osteoporosis

A bone density test is an X-ray that estimates how dense your bone mineral is, which can reveal your risk of fractures. For most people, doctors recommend bone density tests for all women over age 65 and men over age 70, according to the National Osteoporosis Foundation.

Those recommendations vary based on your personal risk factors. “If you’re menopausal, and you’re between the ages of 50 and 65, and you have risk factors, it’s also appropriate to do bone density testing,” says Dr. Chaudhry.

Risk factors for osteoporosis include:

  • Early menopause

  • History of eating disorders

  • History of skipped periods

  • Family history of osteoporosis

  • Celiac disease

  • Inflammatory bowel disease

  • Smoking

  • Or consuming more than two alcoholic drinks a day.

Having any risk factors for osteoporosis could make you eligible for a bone density test as early as age 50.

Understanding Bone Density Test Results

A bone density test will provide a T-score and a Z-score. The T-score compares your bone density to that of a younger, healthy adult; a Z-score compares your bone density to what is normal in someone your age and body size.

Here’s how doctors interpret a T-score from a bone density test:

  • A T-score greater than -1 indicates a normal bone density.

  • A T-score between -1 and -2.5 indicates low bone mass, known as osteopenia. Your doctor may recommend certain lifestyle habits to manage osteopenia.

  • A T-score lower than -2.5 indicates osteoporosis. Your doctor will recommend treatment for osteoporosis to reduce your risk of fracture.

Your T-score may not tell the whole story, especially for younger people (such as women who are still having periods). This is when Z-scores may be more informative.

If someone has a Z-score below -2.5, doctors will likely look for secondary causes of low bone density, such as:

  • Hyperthyroidism

  • Hyperparathyroidism

  • Blood disorders

  • Or excess calcium excreted through the urine.

“Screening is really important because you don’t ‘feel’ osteoporosis,” says Dr. Chaudhry. “You don’t know that it’s there unless you have the test—unless you have a fracture.”