What are the management steps for a patient with elevated 25-hydroxyvitamin D (25(OH)D) levels of 113.2 ng/mL, not taking vitamin D supplements, and experiencing fluctuations?

Management of Unexplained Elevated Vitamin D Levels

Immediately discontinue any potential sources of vitamin D supplementation and investigate for underlying causes of hypervitaminosis D, as a 25(OH)D level of 113.2 ng/mL exceeds the upper limit of normal and approaches the threshold for vitamin D toxicity (>100 ng/mL). 1

Understanding the Clinical Significance

Your patient's vitamin D level of 113.2 ng/mL is substantially elevated:

• Normal range: 20-60 ng/mL for the general population 1
• Sufficiency threshold: ≥30 ng/mL 2, 1
• Toxicity risk: >100 ng/mL, with life-threatening intoxication possible 1
• Your patient's level: 113.2 ng/mL—dangerously close to toxic range

The fluctuating nature of these levels without supplementation is particularly concerning and warrants thorough investigation.

Immediate Management Steps

1. Verify the Elevation and Rule Out Laboratory Error

• Repeat 25(OH)D measurement using a validated assay that detects both vitamin D2 and D3 forms 3
• Confirm the patient is truly not taking any vitamin D supplements, including multivitamins (which typically contain 400 IU) 2
• Review all medications and over-the-counter supplements for hidden vitamin D sources

2. Assess for Symptoms and Complications of Hypervitaminosis D

Monitor serum calcium and phosphorus immediately 4, 2:

• Hypercalcemia is the primary concern with vitamin D toxicity
• Discontinue all vitamin D therapy if serum calcium exceeds 10.2 mg/dL 4
• Check serum phosphorus; if it exceeds 4.6 mg/dL, this compounds the risk 4

Clinical manifestations to assess:

• Hypercalcemia symptoms: nausea, vomiting, weakness, confusion, polyuria, polydipsia
• Renal complications: nephrocalcinosis, nephrolithiasis
• Cardiovascular effects: arrhythmias, vascular calcification

3. Investigate Underlying Causes

Since the patient denies supplementation, consider these etiologies:

Granulomatous diseases (most common cause of non-supplemental hypervitaminosis D):

• Sarcoidosis—extrarenal production of 1,25(OH)₂D by activated macrophages
• Tuberculosis
• Other granulomatous conditions

Malignancies:

• Lymphomas (particularly Hodgkin's and non-Hodgkin's)
• Dysgerminomas
• These can produce ectopic 1α-hydroxylase

Primary hyperparathyroidism:

• Can increase 1,25(OH)₂D production
• Check intact PTH levels

Excessive sun exposure:

• While a 10-15 minute whole-body exposure can generate up to 20,000 IU vitamin D3 5, sustained extreme exposure would be required
• Consider occupational or recreational patterns

Dietary sources:

• Excessive consumption of fortified foods
• High intake of fatty fish, cod liver oil

Monitoring Protocol

Immediate (within 1 week):

• Serum calcium (corrected total calcium) 4
• Serum phosphorus 4
• Intact PTH 4
• Basic metabolic panel (assess renal function)
• Urinalysis (check for hypercalciuria)

Follow-up (every 3 months until normalized) 4, 2:

• Repeat 25(OH)D levels
• Serum calcium and phosphorus
• Renal function monitoring

Diagnostic workup for underlying causes:

• Chest X-ray or CT (evaluate for sarcoidosis, lymphoma)
• Serum ACE level (if sarcoidosis suspected)
• Consider tissue biopsy if granulomatous disease suspected

Treatment Approach

If Calcium is Elevated (>10.2 mg/dL):

Immediate interventions 4:

• Discontinue all vitamin D sources completely
• Increase oral hydration
• Consider loop diuretics (furosemide) to enhance calcium excretion
• Avoid thiazide diuretics (they increase calcium reabsorption)
• Reduce dietary calcium intake temporarily
• Consider glucocorticoids if granulomatous disease is confirmed (they inhibit extrarenal 1α-hydroxylase)

If Calcium is Normal but 25(OH)D Remains Elevated:

• Avoid all vitamin D supplementation 4
• Limit sun exposure 2
• Monitor calcium levels every 3 months 4
• Address underlying cause once identified

Common Pitfalls to Avoid

• Don't assume the patient is being truthful about supplementation: Carefully review all medications, including those prescribed by other providers, over-the-counter supplements, and fortified foods 2
• Don't ignore fluctuating levels: This pattern suggests either intermittent exposure or an underlying disease process with variable activity
• Don't delay calcium monitoring: Hypercalcemia is the dangerous complication, not the elevated 25(OH)D itself 4, 1
• Don't use active vitamin D sterols (calcitriol) for any reason in this patient 4
• Don't overlook granulomatous diseases: These are the most common non-iatrogenic cause of vitamin D elevation

Target Goals

• Reduce 25(OH)D to <60 ng/mL (upper limit of normal range) 1
• Maintain serum calcium <10.2 mg/dL 4
• Maintain serum phosphorus <4.6 mg/dL 4
• Identify and treat underlying cause to prevent recurrence

The fluctuating nature without supplementation strongly suggests an underlying pathological process requiring investigation rather than simple over-supplementation.