This was my experience, as well.My calcium level sort of hung out about 10.2 for several months and then it jumped up to 11.5. At that point, there was no question about it, I needed surgery pretty quickly. High calcium can have serious consequences. It can even cause cardiac arrest. So, off to surgery I went. It turned out that 2 of my 4 parathyroid glands had large benign tumors in then. It was simple as just taking out the 2 bad ones and leaving the good ones in. Within minutes of removing the bad glands, my calcium was back down to 9.6.
Now, I just see my endocrinologist every 6 months and I have my calcium checked every 3-6 months. There is a small 1" scar at the base of my throat. It was swollen and reddened for a few months after surgery, which I hated, but it's been about 16 months now and the scar is very small and silvery, so it's not so noticeable. My vitamin D and calcium levels have been normal for a year and I no longer have to take calcium; I take 2000iu Vit D twice a week, only.