What is the appropriate workup for a 46-year-old male with elevated vitamin D (Vit D) levels of 68.5, who denies taking any vitamin D supplementation?

Workup for Elevated Vitamin D Level (68.5 ng/mL) Without Supplementation

For a 46-year-old male with a vitamin D level of 68.5 ng/mL who denies supplementation, no immediate intervention is required as this level falls within the optimal range (30-80 ng/mL), but investigation of the source is warranted to rule out occult supplementation or underlying pathology. 1

Initial Assessment and Risk Stratification

Your patient's vitamin D level of 68.5 ng/mL is not toxic and does not require urgent intervention. 1 The upper safety limit is 100 ng/mL, and toxicity typically only occurs above 150 ng/mL. 1, 2 However, since the patient denies supplementation, you need to investigate the source of this elevation.

Immediate Laboratory Workup

Measure serum calcium immediately to determine if this represents vitamin D-mediated hypercalcemia or a benign finding. 1 This is the single most important test to guide your next steps.

• If serum calcium is elevated (>10.2 mg/dL): Check intact parathyroid hormone (PTH) to differentiate between vitamin D toxicity (suppressed PTH) and primary hyperparathyroidism (elevated or inappropriately normal PTH). 1, 3
• If serum calcium is normal: This is reassuring and suggests the elevated vitamin D is not causing harm. 1

Check serum phosphorus as well, as abnormalities can indicate underlying metabolic disorders. 4

Investigating the Source of Elevation

Hidden Supplementation Sources

Question the patient specifically about:

• Multivitamins: Patients often don't consider these "vitamin D supplements" but they typically contain 400-1000 IU of vitamin D. 1
• Prescription medications: Some calcium supplements contain vitamin D. 1
• Over-the-counter calcium/vitamin D combinations: Many patients take these for bone health without recognizing them as vitamin D supplementation. 1

Dietary Sources

Assess dietary intake of:

• Fortified milk: Consumption of >3 cups daily correlates with elevated vitamin D levels. 4, 1
• Fortified cereals: These can contribute significant vitamin D. 1
• Fatty fish (salmon, mackerel, sardines): Regular consumption can elevate levels. 1
• Cod liver oil: This is a particularly concentrated source. 1

Sun Exposure

Evaluate sun exposure patterns: Prolonged sun exposure can produce vitamin D equivalent to 20,000 IU daily, though levels rarely exceed 100 ng/mL from sun alone. 1 Ask about:

• Outdoor occupation or recreational activities
• Recent tropical vacation
• Use of tanning beds

Underlying Medical Conditions

Screen for conditions that increase vitamin D conversion:

• Granulomatous diseases: Sarcoidosis, tuberculosis, and other granulomatous conditions can cause elevated vitamin D through increased conversion of 25(OH)D to active 1,25-dihydroxyvitamin D by activated macrophages. 1
• Lymphomas: Particularly Hodgkin's and non-Hodgkin's lymphoma can produce similar effects. 1
• Primary hyperparathyroidism: This can coexist with elevated vitamin D and cause hypercalcemia. 1

Recommended Diagnostic Algorithm

Step 1: Measure serum calcium and phosphorus immediately. 1, 4

Step 2: If calcium is elevated, measure intact PTH. 1

Step 3: Conduct detailed medication and dietary history focusing on hidden vitamin D sources. 1

Step 4: If no obvious source is identified and calcium is normal, consider:

• Chest X-ray to screen for sarcoidosis or lymphoma 1
• Serum ACE level if sarcoidosis is suspected 1
• PTH level even if calcium is normal, to rule out early hyperparathyroidism 1

Step 5: Recheck vitamin D level in 2-3 months to assess trend. 1 If levels are stable and calcium remains normal, this likely represents a benign finding from dietary sources or sun exposure.

Management Based on Findings

If Calcium is Normal and No Pathology Identified

• No treatment is required. 1 The level of 68.5 ng/mL is within the optimal range of 30-80 ng/mL. 1
• Counsel the patient to avoid starting vitamin D supplementation, as they clearly don't need it. 1
• Recheck in 3-6 months to ensure stability. 1

If Hypercalcemia is Present

• Discontinue all vitamin D sources immediately (including dietary fortified foods temporarily). 1
• Limit calcium intake temporarily until vitamin D levels normalize. 1
• Monitor serum calcium closely until levels return to normal. 1
• Consider intravenous hydration and loop diuretics if hypercalcemia is symptomatic or severe (>12 mg/dL). 1

If Underlying Disease is Identified

• Granulomatous disease: Treat the underlying condition; vitamin D levels will normalize with disease control. 1
• Lymphoma: Refer to oncology for appropriate management. 1
• Primary hyperparathyroidism: Refer to endocrinology for parathyroid evaluation. 1

Common Pitfalls to Avoid

• Don't assume the patient is being truthful about supplementation initially. Many patients genuinely don't realize they're taking vitamin D in multivitamins or calcium supplements. 1
• Don't panic about the level of 68.5 ng/mL. This is well below the toxicity threshold of 100 ng/mL and within the optimal range. 1, 2
• Don't order extensive workup if calcium is normal and dietary/sun exposure sources are identified. This is likely a benign finding. 1
• Don't forget to check calcium. This is the key test that determines whether the elevated vitamin D is causing harm. 1
• Don't measure 1,25-dihydroxyvitamin D routinely. The 25(OH)D level is the appropriate test for nutritional status. 3

Long-term Monitoring

If no pathology is identified and calcium remains normal, recheck vitamin D annually to ensure levels don't continue to rise. 3 If levels remain stable in the 30-80 ng/mL range, no further intervention is needed. 1