How osteoporosis is detected

Osteoporosis is found through a bone density scan, not through blood work or symptoms. The standard test is called a DXA scan (dual-energy X-ray absorptiometry), which measures how much mineral is packed into your bones. It takes about 10 to 30 minutes, uses a very small dose of radiation—less than a chest X-ray—and produces a number called a T-score that tells you how your bone density compares to a healthy young adult's.

You cannot feel osteoporosis developing, and most people have no symptoms until a bone breaks. That is why screening exists: to find low bone density before a fracture happens, when treatment can still prevent one. A DXA scan is the only way to know whether your bones are thinning.

Key Takeaways

  • A DXA scan is the standard test for osteoporosis and takes 10 to 30 minutes with minimal radiation exposure.
  • Your T-score tells you how your bone density compares to a healthy young adult, and scores below -2.5 indicate osteoporosis.
  • Screening is recommended for all women at age 65, all men at age 70, and younger people with risk factors like fracture history or long-term steroid use.
  • If your first scan shows low bone density, a second scan in one to two years helps determine whether your bones are getting weaker.

Who should get screened and when

The U.S. Preventive Services Task Force recommends screening for all women at age 65 and all men at age 70. Younger people should be screened if they have risk factors: a personal history of fracture as an adult, a parent or sibling with hip fracture, current smoking, heavy alcohol use, long-term use of corticosteroids (such as prednisone), or conditions that affect bone metabolism like rheumatoid arthritis or celiac disease.

Women who have gone through menopause but are younger than 65 should discuss screening with their doctor if they have any of those risk factors. Bone loss accelerates in the years right after menopause, so earlier screening sometimes makes sense. Your doctor can assess your individual risk and recommend whether a scan would be useful for you.

What happens during a DXA scan

You lie on a padded table while an arm moves slowly across your lower spine and hip—the two places where fractures from osteoporosis are most common and most serious. You wear regular clothes and remove metal objects like jewelry or a belt. The machine sends a low-energy X-ray beam through the bone, and a detector on the other side measures how much radiation passes through. Denser bone blocks more radiation, so the machine can calculate bone mineral density from the difference.

The scan is painless and you do not have to hold your breath or stay still in an uncomfortable position. Some facilities also scan the forearm or the whole body, depending on your situation. The radiologist or technician will give you the results, usually within a few days, along with a report your doctor will review with you.

Understanding your T-score

Your T-score is the number of standard deviations your bone density is above or below the average for a healthy 30-year-old. The categories are:

  • T-score -1.0 or higher: Normal bone density.
  • T-score between -1.0 and -2.5: Low bone density, called osteopenia. Your bones are thinner than normal but not yet in the osteoporosis range.
  • T-score -2.5 or lower: Osteoporosis. Your bones are significantly weaker and fracture risk is elevated.

A T-score is only one piece of the picture. Your doctor will also consider your age, sex, whether you have had a fracture, and other health conditions. Two people with the same T-score may have different fracture risk depending on these other factors. Your doctor may calculate a 10-year fracture risk using a tool called FRAX, which combines your T-score with other information to estimate your actual chance of breaking a hip or spine in the next decade.

What happens after your first scan

If your scan shows normal bone density, you typically do not need another scan for 10 years. If you have osteopenia, your doctor will usually recommend a repeat scan in one to two years to see whether your bone density is stable or declining. If you have osteoporosis, your doctor will discuss treatment options and may recommend a repeat scan one to two years after you start treatment to see whether the medication is slowing bone loss.

Repeat scans are important because a single low score does not tell you whether your bones are getting weaker. Some people's bone density stays the same for years; others lose density quickly. A second scan shows the trend, which helps your doctor decide whether treatment is working or whether a different approach is needed.

Other tests that may accompany a DXA scan

Your doctor may order blood work to check for conditions that cause bone loss, such as vitamin D deficiency, thyroid disease, or kidney problems. A 25-hydroxyvitamin D test is common because low vitamin D weakens bones and is easily corrected. If you are a woman past menopause or a man over 70, your doctor may also check calcium and kidney function to make sure your body can handle calcium supplements if they are recommended.

In some cases, your doctor may order additional imaging—such as an X-ray of your spine—if you have had a height loss or back pain, to check whether you have already had a compression fracture without knowing it. These fractures can happen silently and are a sign that treatment should start right away.

Preparing for your scan and what to bring

You do not need to fast or stop taking medications before a DXA scan. Wear loose, comfortable clothing without metal zippers, snaps, or underwire. Remove jewelry, watches, and anything else metal. If you have had a CT scan, MRI, or nuclear medicine scan with contrast dye in the past week, tell the facility—contrast can interfere with the measurement.

Bring your insurance card and a photo ID. If you have had previous DXA scans at another facility, ask that facility to send the images to your current one. Comparing scans from the same machine over time is more accurate than comparing scans from different machines, so your doctor will want the earlier images if they exist.

Frequently Asked Questions

Is the radiation from a DXA scan dangerous?

No. A DXA scan uses about one-tenth the radiation of a chest X-ray and one-hundredth of a CT scan. The benefit of finding osteoporosis before a fracture far outweighs the tiny radiation risk. Pregnant women should not have a DXA scan, but for everyone else, the radiation dose is considered safe.

Can I get a DXA scan without a doctor's order?

Most imaging centers require a doctor's order to perform a DXA scan. Some facilities offer screening scans directly to the public, but your insurance may not cover the cost without a physician referral. Talk to your primary care doctor about whether screening makes sense for you.

What if my T-score is between -1 and -2.5?

This range is called osteopenia, and it means your bones are thinner than normal but not yet at the threshold for osteoporosis. Your doctor will recommend lifestyle changes—weight-bearing exercise, adequate calcium and vitamin D, no smoking—and may suggest a repeat scan in one to two years to track whether density is declining.

How often do I need to be rescanned?

If your bone density is normal, rescanning every 10 years is standard. If you have osteopenia, every one to two years is typical. If you have osteoporosis and are on treatment, your doctor may rescan after one to two years to see whether the medication is working, then every two years after that.

Can osteoporosis be seen on a regular X-ray?

Not reliably. A regular X-ray can show severe osteoporosis or a fracture, but it cannot detect mild to moderate bone loss the way a DXA scan can. That is why DXA is the standard screening tool—it catches the problem early, before a break happens.