a-60-year-old-patient-taking-long-term-proton-pump-inhibitors-develops-fatigue-a

Question

A 60-year-old patient taking long-term proton pump inhibitors develops fatigue and paresthesias. You suspect B12 deficiency due to impaired absorption. Which laboratory pattern would best support this diagnosis?

Accepted Answer

Low serum B12, elevated methylmalonic acid, and elevated homocysteine — consistent with B12 deficiency from reduced gastric acid/intrinsic factor function.

Answer

Elevated urinary biotin and undetectable serum vitamin C, which are specific indicators of B12 deficiency due to drug interactions.

Answer

Low serum niacin with markedly elevated LDL cholesterol and decreased HDL, which is the hallmark lab pattern of B12 malabsorption.

Answer

High serum folate with low methylmalonic acid and normal homocysteine, indicating pure folate toxicity rather than B12 deficiency.