Vitamin D Supplementation with Ionized Calcium 6.5 mg/dL and Vitamin D 33 ng/mL
You should NOT continue vitamin D supplementation with an ionized calcium of 6.5 mg/dL (1.62 mmol/L), as this represents significant hypercalcemia that requires immediate discontinuation of all vitamin D therapy and treatment of the elevated calcium. 1
Understanding Your Calcium Level
An ionized calcium of 6.5 mg/dL (1.62 mmol/L) is severely elevated, as normal ionized calcium ranges from approximately 4.6-5.3 mg/dL (1.15-1.32 mmol/L). 2
This level of hypercalcemia can cause serious symptoms including nausea, vomiting, confusion, kidney damage, and cardiac arrhythmias. 2
Severe hypercalcemia is defined as ionized calcium ≥10 mg/dL (≥2.5 mmol/L) or total calcium ≥14 mg/dL, but your level of 6.5 mg/dL still represents clinically significant elevation requiring intervention. 2
Why Vitamin D Must Be Stopped
The K/DOQI guidelines explicitly state that if serum calcium exceeds 10.2 mg/dL (approximately 5.1 mg/dL ionized), you must discontinue ergocalciferol therapy and ALL forms of vitamin D therapy immediately. 1
Vitamin D supplementation—even at your "insufficient" level of 33 ng/mL—can worsen hypercalcemia by increasing intestinal calcium absorption and mobilizing calcium from bone. 3, 4
The FDA drug label for vitamin D warns that hypervitaminosis D causes hypercalcemia with serious complications including vascular calcification, nephrocalcinosis, and irreversible renal insufficiency. 3
Your Vitamin D Level Does Not Change This Decision
While your 25-hydroxyvitamin D level of 33 ng/mL is technically in the "sufficient" range (>30 ng/mL), this is irrelevant when hypercalcemia is present. 1
The presence of hypercalcemia is an absolute contraindication to vitamin D supplementation, regardless of your vitamin D level. 1
Correcting vitamin D deficiency can only be considered AFTER your calcium has normalized and the underlying cause of hypercalcemia has been identified and treated. 1
Immediate Management Required
Stop all vitamin D supplements immediately (including multivitamins containing vitamin D, prescription vitamin D, and over-the-counter supplements). 1, 3
Limit total calcium intake from all sources (diet plus any supplements) to no more than 2,000 mg/day, and consider reducing calcium-containing foods temporarily. 1
Increase fluid intake significantly to promote urinary calcium excretion and prevent kidney stone formation. 3, 2
Contact your physician urgently for evaluation, as you may need intravenous hydration with saline and possibly loop diuretics to lower your calcium level. 3, 2
Investigation Needed
Your doctor should measure serum PTH (parathyroid hormone) to determine if this is PTH-dependent hypercalcemia (primary hyperparathyroidism) or PTH-independent (from another cause). 2, 5
Check serum phosphorus, as the calcium-phosphorus product should be maintained at <55 mg²/dL² to prevent tissue calcification. 1
Evaluate kidney function (creatinine, eGFR) as hypercalcemia can cause acute kidney injury. 1, 2
Consider checking 1,25-dihydroxyvitamin D levels if granulomatous disease or lymphoma is suspected as a cause of hypercalcemia. 4
Common Pitfall to Avoid
Do not assume that "low" vitamin D justifies supplementation when calcium is elevated. This is a dangerous misconception that can lead to worsening hypercalcemia, kidney damage, and vascular calcification. 1, 3
Vitamin D can only be safely restarted once calcium normalizes (ideally <9.5 mg/dL total or <5.0 mg/dL ionized), the underlying cause is identified, and your physician provides specific guidance with close monitoring. 1