Is there a way to test calcitonin levels, or for hypoparathyroidism? Also, is there some kind of parathyroidism replacement therapy?

Tests for. calcitonin and parathyroid hormone are readily available. The most common test would be measurement of your calcium, and (if necessary) ionized calcium. Vitamin D should also be evaluated. There are treatments for hypopara, but why do you think you have it? Calcitonin is not a part of hypopara. Check w/your doctor,
YES YOU CAN. Yes you can check Calcitonin level in blood and it is not done for Hypoparathyroidism There is no Parathyroid replacement therapy and Hypoparathyroidism is treated with oral Calcium and Vitamin D.