Over the last 5 months my calcium levels have been above 10.0 mg/dl, up to 10.3 mg/dl. My doctor tells me this is normal. I'm 75 years old, and my calcium levels before this were always between 9.1 and 9.7 mg/dl. Why is my calcium rising?
At your age, a calcium of 10.3 mg/dl (2.57 mmol/l) is too high. Most adults over about age 40 should have calcium levels in the mid to high 9s, up to 10.0 mg/dl (2.5 mmol/l). Sometimes adults in their 40s will still have calcium levels in the low 10s, but generally these levels drop as you age. By the time you are 75, you should not have any calcium levels above 10.0, especially if your calcium was in the normal range prior to 5 months ago.
High calcium levels like yours are usually caused by primary hyperparathyroidism (usually the result of a benign parathyroid tumor). This has to be confirmed with a PTH test - if the PTH is high or in the “normal” range, with a high calcium, then primary hyperparathyroidism can be diagnosed. Primary hyperparathyroidism is treated with surgery to remove the diseased parathyroid glands.