Mastitis metritis agalactia (MMA) is a common disease in post‐partum sows and has a negative effect on sows' longevity as well as on sows' and piglets' health. MMA leads to an inflammatory state. The aim was to investigate the impact of MMA on bone and fat metabolism. The hypothesis was that it is possible to predict MMA by measuring ketone bodies and bone markers. Blood samples from 175 sows were taken within 72 hr after farrowing. Serum was analysed for 25‐hydroxyvitamin D (25‐(OH)‐D), serum crosslaps (CTX‐I), osteocalcin (OC), alkaline phosphatase (ALP), calcium (Ca), magnesium (Mg), phosphorus (P), parathyroid hormone (PTH), triglycerides (TG), beta‐hydroxybutyric acid (BHB), tumour necrosis factor‐alpha (TNF‐α) and haptoglobin. Spontaneous urine was collected, and pH value was measured in addition to Ca and P. A proximate analysis of the sows' diets was performed. Age, litter size, body condition score (BCS) and clinical signs of MMA were recorded for each sow. A multivariable logistic regression was undertaken with disease status (MMA or healthy) as the dependent variable. Significance was accepted at p <.05. MMA sows had a poorer BCS (p <.001) in relation to healthy sows. Age and number of piglets did not differ. MMA sows showed increased serum CTX‐I (p =.004) and decreased serum OC (p <.001). Concentrations of P (p =.007), activity of ALP (p =.002) and BHB (p =.019) as well as TNF‐α (p <.001) and haptoglobin (p =.048) concentrations were increased in MMA sows. No difference in urinary pH value between MMA and healthy sows was found. Our results are in accordance with the known fact that sows are in an extreme catabolic state peripartum. Bone metabolism in MMA sows is much more negatively affected than in healthy sows post‐partum, due to inflammatory processes shown by higher concentrations of pro‐inflammatory cytokines. [ABSTRACT FROM AUTHOR]