A bone density test for women is a quick, painless scan that measures how strong your bones are. The standard method is called a DXA scan (sometimes written as DEXA), which uses a very low dose of X-rays to measure bone mineral density at the hip and spine. The whole process typically takes 10 to 30 minutes, requires no injections or dye, and feels similar to having a regular X-ray.
What Happens During the Scan
You lie on your back on a flat, open X-ray table. There’s no tunnel or enclosed space, so it’s nothing like an MRI. A large scanning arm passes slowly over your body, directing a thin beam of low-dose X-rays through the areas being measured. You won’t feel the beam at all.
The technologist will position you in two ways during the scan. To measure your spine, your legs are raised onto a padded box that flattens your lower back against the table. To measure your hip, your foot is placed in a small brace that rotates the hip slightly inward. In both positions, the detector glides over the area and sends images to a computer screen. You need to stay still during each pass and may be asked to hold your breath briefly, just as you would for a chest X-ray.
Most scans wrap up in 10 to 20 minutes. You can get up and go about your day immediately afterward with no recovery time and no side effects.
How to Prepare
Preparation is minimal, but a few things matter. Stop taking calcium supplements at least 24 hours before the test, because undigested calcium in your system can skew the readings. Wear loose, comfortable clothing without zippers, belts, or metal buttons. Leave jewelry at home and empty metal items like keys and coins from your pockets. Some facilities will have you change into a gown, but many won’t if your clothing is free of metal.
If you’ve recently had a CT scan or barium study that used contrast material, let your doctor know before scheduling. Residual contrast in your body can interfere with the X-ray measurements, so you may need to wait before having the DXA done.
Who Should Get Tested
The U.S. Preventive Services Task Force recommends routine bone density screening for all women 65 and older. Postmenopausal women younger than 65 are also recommended for screening if they have additional risk factors for osteoporosis. Those risk factors include low body weight, a parent who fractured a hip, cigarette smoking, and excess alcohol consumption.
If you fall into that younger group, your doctor will typically use a risk assessment tool that weighs your individual factors to determine whether screening makes sense for you now or can wait.
Peripheral Screening Tests
You may encounter smaller, portable devices at pharmacies or health fairs that measure bone density in your wrist, finger, or heel. These peripheral tests are faster and cheaper, but they don’t measure the hip and spine, which are the sites most vulnerable to osteoporotic fractures. A central DXA scan of the hip and spine is the standard used to formally diagnose osteoporosis and guide treatment decisions. A peripheral test can flag potential concerns, but a central DXA is typically needed to confirm or rule out a diagnosis.
Understanding Your Results
Your results come as a number called a T-score, which compares your bone density to that of a healthy 30-year-old woman at peak bone mass. The scale works like this:
- T-score of -1.0 or higher: Normal bone density.
- T-score between -1.0 and -2.5: Osteopenia, meaning bone density is lower than normal but not yet in the osteoporosis range. This is common in postmenopausal women and often managed with lifestyle changes like weight-bearing exercise and adequate calcium and vitamin D intake.
- T-score of -2.5 or lower: Osteoporosis, indicating significantly reduced bone density and a higher risk of fractures.
The further your T-score falls below zero, the lower your bone density and the greater your fracture risk. A score of -3.0, for example, represents more bone loss than -2.5. Your doctor will look at your T-score alongside your age, fracture history, and other health factors to decide whether treatment is needed or whether monitoring over time is the better approach.
Radiation Exposure
DXA scans use a fraction of the radiation involved in a standard chest X-ray. The dose is extremely low, which is one reason the test is considered safe enough for routine screening and repeat scans every one to two years when monitoring is needed. There are no lingering effects, and you don’t need to take any precautions around others afterward.