Blood magnesium and the renal magnesium threshold in lichen-fed and fasted reindeer.

In the blood plasma of lichen-fed reindeer the magnesium level was rather low (1.44 +/- 0.17 mg/100 ml) while the levels of calcium, phosphorus and glucose were normal. Fasting for 2--3 days provided no evidence of magnesium deficiency, leading to increments in blood and urinary magnesium. Simultaneous increments in urinary calcium indicated mobilization of bone minerals. The renal magnesium threshold appeared to be at about 1.8 mg of Mg/100 ml of plasma as in other species.