ObjectiveCorrelate serum magnesium (Mg) and Calcium (Ca) levels with body composition and metabolic parameters in women with fibromyalgia (FM).Patients and methodsCross-sectional study compared with a control group paired by age and body mass index (BMI) of adult women diagnosed with fibromyalgia. All participants went through assessment of their body composition through dual-energy X-ray absorptiometry (DXA) and had blood samples collected for dosing of Mg, Ca, C-reactive Protein (CRP), lipidogram and glycemia. Results: 53 women with FM (average age 48.1 ± 8.2 years, average BMI 26.6 ± 4.5 kg/m2) and 50 control women (average age 47.1 ± 9.9 years, average BMI 25.6 ± 3.6 kg/m2) participated in the study. Serum levels turned out to have inverse correlation with CRP in the FM group (r = − 0.29, p = 0.03) and with BMI and glycemia in the control group (r = 0.31; p = 0.02 and r = 0.48; p = 0.0004 respectively). Serum levels of calcium correlated with triglycerides (r = 0.29; p = 0.03) in the FM group and with glycemia in the control group (r = 0.64; p = 0.0001).ConclusionsIn patients with FM, magnesemia turned out to have inverse correlation with CRP and calcemia had positive association with triglycerides.