Preparing for a bone density test is straightforward, and the most important step is stopping calcium supplements at least 24 hours beforehand. Beyond that, the prep is mostly about what you wear and what recent medical procedures you may have had. The test itself is painless, noninvasive, and typically takes 10 to 30 minutes.
Stop Calcium Supplements 24 Hours Before
This is the single most important preparation step. Calcium supplements and any over-the-counter vitamins containing calcium should be paused at least 24 hours before your scan. Residual calcium in your system can artificially inflate your bone density reading, which defeats the purpose of the test. Regular food is fine, and you do not need to fast. Eat and drink normally on the day of your appointment.
If you take prescription osteoporosis medications, keep taking them as directed unless your doctor specifically tells you otherwise. The 24-hour restriction applies to supplements, not prescribed treatments.
Wear the Right Clothing
Metal interferes with the low-dose X-ray beam used during the scan, so your clothing choices matter more than you might expect. The CDC advises avoiding anything with metal buckles, buttons, or zippers. That rules out most jeans, belted pants, and bras with underwire or metal hooks.
Your best option is soft, comfortable clothing with elastic waistbands: sweatpants, yoga pants, or athletic shorts paired with a simple T-shirt or pullover. Skip the sports bra with a metal clasp too. If you forget and show up in jeans, the facility will likely ask you to change into a gown, which can add time to your visit.
Leave jewelry at home, especially belly button piercings, necklaces, and anything around your waist or hips. You may also be asked to remove eyeglasses during the scan.
Wait 7 Days After Contrast Procedures
If you’ve recently had a barium swallow study, a CT scan with contrast dye, or an MRI with contrast injection, you need to wait at least 7 days before having your bone density test. These contrast materials linger in your body and can distort the scan results. When scheduling your appointment, mention any imaging procedures you’ve had in the past two weeks so the facility can confirm the timing works.
Know What Happens During the Scan
A bone density test, formally called a DXA or DEXA scan, measures how dense and strong your bones are using a very low dose of radiation, far less than a standard chest X-ray. The machine scans your lower spine and one or both hips, since these are the areas most vulnerable to osteoporosis-related fractures.
You’ll lie flat on your back on a padded table while the scanner passes over you. It doesn’t touch you, and you won’t feel anything. The key requirement is staying still for the duration, which is usually under 20 minutes total. If you have difficulty lying flat due to back pain or other conditions, let the facility know when you schedule so they can accommodate you.
There’s no recovery time. You’ll get up and go about your day immediately after. Results are reported as a T-score, which compares your bone density to that of a healthy 30-year-old. Your doctor will walk you through what your score means and whether any follow-up is needed.
Quick Checklist the Day Before
- 24 hours before: Stop all calcium supplements and multivitamins containing calcium.
- Morning of: Eat and drink normally. No fasting required.
- Getting dressed: Choose metal-free clothing with elastic waistbands. Leave jewelry at home.
- At check-in: Mention any recent contrast imaging procedures, and let staff know if you could be pregnant, since the test uses a small amount of radiation.