- Hypo-parathyroid in patients s/p parathyroid or thyroid surgery
- Severe vitamin D deficiency (e.g. CKD where low 1,25 Oh), low calcium intake
- XRT to parathyroid area
- Resistance to Vitamin D, idiopathic
- S/P gastric by-pass
- Numbness/tingling peri-oral or upper extremities
- Weakness, muscle cramps