Approach Considerations
Acetaminophen and aspirin levels should be assessed in every suspected ingestion. Electrolyte levels must be assessed in patients with severe vomiting or diarrhea.
In addition to laboratory studies, imaging and electrocardiographic studies can be used in the assessment of patients with vitamin toxicity.
Imaging Studies
Imaging studies can be employed as follows:
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Skeletal radiography - For calcifications in chronic vitamin A and vitamin D toxicity
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Hand radiography - For periosteal calcifications
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Helical computed tomography (CT) scanning and urography - Obtain a helical CT scan or an intravenous urogram (IVU) for suspected nephrolithiasis (ie, oxalate stones) in patients with vitamin C toxicity
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CT scanning of the brain - In the presence of neurologic abnormalities, perform a CT scan of the brain, without contrast, only if the prothrombin time (PT) is significantly prolonged and the patient has either a decreased level of consciousness or a focal neurologic deficit
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Kidneys, ureters, bladder (KUB) film - Indicated for suspected toxicity from iron-containing pills
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Bone mineral density testing - to evaluate the effect of long-term vitamin A intoxication on reducing bone density and causing osteoporosis [48]
Electrocardiography
Obtain an electrocardiogram (ECG) to evaluate for effects of hypercalcemia in patients with vitamin D toxicity.
Laboratory Studies
Vitamin A
The reference range for vitamin A is 20-60 mcg/dL, and a toxic level is higher than 60-100 mcg/dL. Obtain a complete blood count (CBC) to rule out leukopenia. Also perform calcium, glucose, and liver function tests (LFTs). levels are affected by liver stores and dietary intake of vitamin A.
For serum carotene, the normal range is 50-300 mcg/dL. Carotene levels reflects dietary intake of vitamin A.
Laboratory studies in vitamin A toxicity include the following:
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Serum electrolytes - If vomiting or diarrhea is present
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Serum calcium - Hypercalcemia may be observed [42]
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Liver function tests (LFTs)
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Complete blood count (CBC) - For anemia, leukopenia, or thrombocytopenia
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Vitamin A assessment by serum retinol concentrations - Vitamin A assessment by serum retinol concentrations may be helpful if the level is markedly high; in mild conditions, however, it may not be sensitive
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High-performance liquid chromatography (HPLC)
Johnson-Davis et al reported that a modified form of HPLC they developed shortened analysis time for serum concentrations of vitamins A and E. [49] Using their modifications—a high-throughput analytic column and small diameter tubing—to determine pediatric reference intervals for the 2 vitamins in 1136 healthy children, the authors found that their technique reduced run-time by 60%, mobile phase consumption by 39%, and sample injection volume by 50%.
A lumbar puncture may be indicated to rule out increased intracranial pressure in patients with vitamin A toxicity.
B Vitamins
Recommended laboratory studies in patients with possible B vitamin toxicity are as follows:
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Vitamins B1, B2, and B12 - These require no specific laboratory tests.
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Vitamin B3 - Perform LFTs. Uric acid may be increased, leading to gouty arthritis. The glucose level is occasionally elevated.
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Vitamin B6 - Vitamin B6 toxicity does not require laboratory or other tests. Lumbar puncture may be considered to rule out other causes if the patient has a peripheral neuropathy.
Vitamin C
Perform urinalysis to rule out uricosuria. False-negative test results for glucosuria are possible. Also perform renal function tests.
Measure PT if the patient is taking warfarin (Coumadin), since vitamin C may interfere with this drug. Serum iron levels should also be measured, because vitamin C enhances iron absorption.
Vitamin D
Obtaining calcium levels is mandatory; they are usually above 11 mg/dL but may be much higher. Phosphate levels may increase with calcium.
Kidney function tests (ie, blood urea nitrogen [BUN] and creatine tests, as well as urinalysis) are necessary to rule out possible kidney damage from hypercalciuria.
Vitamin E
Measure PT, activated partial thromboplastin time (aPTT), and bleeding times, especially if any evidence of bruising or bleeding is present. Platelet aggregation studies may be performed if bleeding time results are abnormal.
Monitor PT in patients who are taking anticoagulants concurrently with vitamin E or in patients suggested to have vitamin K deficiency while taking vitamin E, because the PT may be elevated.
The plasma concentration of alpha tocopherol (normal, 6-14 mcg/mL) can be measured to confirm that high levels of vitamin E are in the blood.
Vitamin K
Measure PT if the patient is taking oral anticoagulants.
