There is no consensus on how to protect the skeleton with adequate supplements in patients who have undergone bariatric operations. The main problem in mineral metabolism is usually related to secondary hyperparathyroidism (2 degrees HPT), often caused by a lack of dietary calcium, magnesium or vitamin D, together with changes in intestinal fermentation, transit time, and resorption surfaces left behind after bariatric operations. After primarily restrictive bariatric surgery, adequate mineral metabolism depends mainly on the active metabolite of vitamin D, whereas after primarily malabsorptive surgery, it depends largely on passive resorption by means of the calcium sensitizing receptor (CaSR). Notably, CaSR-activated calcium transport is coupled to the presence of sufficient magnesium. The current review discusses clinically relevant mechanisms of mineral metabolism and provides recommendations for adequate calcium, magnesium, and vitamin D supplementation. Nevertheless, formal supplementation guidelines are needed in the near future.