A bone density scan, formally known as a Dual-Energy X-ray Absorptiometry (DEXA or DXA) scan, is a quick, non-invasive procedure used to measure bone mineral density (BMD), most commonly in the hip and spine. This measurement is used to assess bone strength, diagnose conditions like osteoporosis, and evaluate the risk of fracture. Preparation is important because certain substances or materials can interfere with the low-dose X-ray technology, leading to inaccurate baseline measurements of your BMD. Following specific guidelines ensures the resulting data is precise, allowing your healthcare provider to make the most informed decisions about your bone health.
Dietary and Supplement Adjustments Before the Scan
The most specific preparation involves temporary changes to your supplement routine, especially those containing calcium. Calcium supplements, including multivitamins and antacids like Tums, must be avoided for a specific period before the scan. This is because undissolved calcium material in the stomach or intestinal tract can temporarily register as high-density material on the X-ray, which could falsely inflate the measured BMD in the spine or hip area.
You should stop taking any calcium-containing supplements for at least 24 hours before your scheduled appointment. Some facilities may recommend a longer window, such as 48 hours, so it is always best to confirm the exact protocol with the scanning center. While supplements must be paused, you can generally continue to eat and drink normally, including consuming foods naturally rich in calcium.
Fasting is not typically required before a DEXA scan, but it is often recommended to avoid consuming a large, heavy meal immediately prior to the test. A substantial amount of food in the digestive tract can potentially create a temporary artifact or slight interference with the scan’s precise measurements. You should also continue to take all prescription medications on your regular schedule, unless your healthcare provider specifically instructs you otherwise.
Essential Preparation on the Day of the Appointment
On the day of your scan, preparation focuses primarily on what you wear and what you bring with you. The DEXA machine relies on dual-energy X-rays, and any metal object in the scanning field can disrupt the image quality and skew the results. Metal absorbs the X-rays differently than bone and soft tissue, appearing as a dense artifact that can artificially alter the BMD reading.
For this reason, you must wear loose, comfortable clothing that is completely free of metal components. This includes avoiding zippers, metal buttons, snaps, belts, and underwire bras. Items with metallic threads or paint should also be avoided, and you may be asked to change into a gown if your clothing contains any of these materials.
All jewelry and metal accessories must be removed before the scan, including necklaces, earrings, watches, and body piercings, especially those located near the trunk of the body. Leaving valuable items at home is the best way to ensure they are not misplaced during the procedure. Additionally, remember to bring necessary administrative items, such as your photo identification and insurance information, to facilitate the check-in process.
Medical History and Timing Considerations
Certain recent medical procedures involving contrast agents can interfere with the accuracy of the DEXA scan, making timing a preparation element. Procedures like CT scans, MRI, or gastrointestinal studies using contrast dye, such as barium, introduce dense materials into the body. These agents can remain in the digestive tract or circulatory system for a period of time.
If a DEXA scan is performed while contrast material is still present, the dual-energy X-ray beams may interpret the dense contrast as bone, leading to a falsely elevated BMD reading. Depending on the type of contrast used, it is generally necessary to wait between three and fourteen days after the procedure before undergoing a DEXA scan. For example, barium studies often require a waiting period of at least seven days.
Another important consideration is pregnancy, as DEXA scans utilize a low dose of ionizing radiation. If there is any possibility of pregnancy, you must inform your healthcare provider and the scanning facility immediately. The procedure will not be performed on pregnant individuals to avoid any radiation exposure to the developing fetus. Openly communicating your recent medical history and pregnancy status ensures the safety and diagnostic reliability of the bone density test.