Taking Magnesium Before a DEXA Scan
Yes, it is safe to take magnesium before a DEXA scan, as oral magnesium supplements do not interfere with bone density measurements. However, timing considerations apply if the magnesium is in tablet form that could create imaging artifacts.
Key Technical Considerations
Tablet Artifacts and Timing
- Undissolved calcium or mineral tablets in the gastrointestinal tract can create artifacts on DEXA scans, but these effects are minimal for overall lumbar spine (L1-4) measurements 1
- Research demonstrates that a 500-mg calcium tablet overlying the spine results in ≤2.2% mean increase in measured BMD for L1-4, which is less than the least significant change threshold and does not alter diagnostic classification 1
- However, tablets overlying a single vertebral body can cause substantial artifacts, with up to 12.6% mean increase in single vertebral BMD, particularly in patients with lower baseline bone density 1
Practical Recommendations
- If taking magnesium tablets, ideally take them several hours before the scan or wait until after the scan to minimize any potential artifact 1
- Modern DEXA software can identify tablets in the soft-tissue field as artifacts and exclude them from analysis, but tablets overlapping both bone and soft tissue may require operator intervention 1
- Liquid or dissolved magnesium formulations pose no interference risk and can be taken at any time before the scan 1
Clinical Context for Magnesium and Bone Health
Magnesium's Role in Bone Density
- Higher magnesium intake is positively associated with hip and femoral neck BMD in older adults 2
- Meta-analysis shows a significant positive association between magnesium intake and hip BMD (pooled beta: 0.03,95% CI: 0.01-0.06, p < 0.05) 2
- Magnesium supplementation may prevent renal stone formation and should be considered in patients with metabolic bone disease 3
Magnesium Deficiency and DEXA Scanning
- Patients with magnesium deficiency (common in those with high-output stomas or malabsorption) should have bone mineral density assessed with DEXA scanning 3
- Hypomagnesemia increases the risk of renal precipitations and may contribute to metabolic bone disease 3
Common Pitfalls to Avoid
- Do not discontinue medically necessary magnesium supplementation before a DEXA scan, as the clinical benefits of maintaining adequate magnesium levels outweigh any minimal artifact risk 3
- If only two or three vertebral levels are available for analysis (rather than L1-4), tablet artifacts could potentially cause misclassification, so timing becomes more important 1
- Be aware that precision of monitoring BMD over time could be affected by tablet artifact if undetected, especially with smaller regions of interest and lower baseline BMD 1
Bottom Line
Take your magnesium as prescribed, but if using tablet formulations, consider taking them several hours before or after the scan to eliminate any possibility of imaging artifact. The actual interference is minimal for standard L1-4 measurements, but this simple timing adjustment provides complete assurance of accurate results 1.