The aim of the research was to assess whether there was a link between serum calcium (Ca) after calving and serum progesterone, milk somatic cells count and Ca, and other blood metabolites in Achai and crossbred cows. Based on blood calcium level shortly after calving, thirty cows from both breeds were divided into a moderate group (≤10.0 mg/dl of Ca) and a high group (>10.0 mg/dl of Ca), with samples collected at 0, 7, 14, 21, 28 and 35 days post-partum, respectively. On day 35 of the post-partum, crossbred and Achai cows with high blood Ca recorded significantly (p < .01) higher serum progesterone, glucose, triglyceride and milk Ca compared with moderate blood Ca group; however, serum cholesterol was significantly (p < .01) higher in both breeds under high blood Ca. Incidence of subclinical mastitis was significantly (p < .01) higher in crossbred and Achai cows under high blood Ca. The results showed that blood progesterone (OR=2.095), glucose (OR=1.024), triglyceride (OR=4.571), cholesterol (OR=1.111) and milk Ca (OR=1.141) resulted in a greater concentration in crossbred compared to Achai cows. A significant (p < .01) correlation was found between blood Ca and other blood metabolites (progesterone, glucose, triglyceride and cholesterol) in both breeds. In conclusion, greater serum Ca concentration after calving is associated with greater serum progesterone, glucose, triglyceride and milk Ca in crossbred cows; however, the incidence of subclinical mastitis increased.