I just found out on routine bloodwork that my calcium is 12.4 mg/dl. I know I need parathyroid surgery but I won't be able to see the surgeon until next month. Since my calcium is so high, I'm worried that my health is going to deteriorate before I get this operation. How quickly do I need to get this done?
The odds are that you have had high calcium levels for years. Your calcium did not jump from normal range to 12.4 in a day, or you likely would have noticed acute symptoms of high calcium (nausea, vomiting, confusion). Since this was found incidentally, it is very likely that you have had rising calcium levels for a while. The severity of primary hyperparathyroidism is unrelated to how high the calcium is, so having a calcium of 12.4 is not necessarily worse for your health than 11.4, or even 10.4. Any high calcium will cause problems over time.
Since you have already had this for a long time, waiting a few months is not going to make a significant difference to your health. Primary hyperparathyroidism is a disease that causes problems over many years, not months. You won’t want to wait more than a year, but a month or two will be fine.
While you are waiting to get the operation, make sure you stay hydrated. Dehydration can raise your calcium level, so be sure to drink lots of fluids. You also want to avoid taking Vitamin D or calcium supplements, which can both raise your calcium level. (Vitamin D deficiency is common in primary hyperparathyroidism, but should not be treated. Vitamin D supplements should not be taken when your calcium is high.)