Which signs are typical of vitamin B12 deficiency?

• A. Shortness of breath and leg cramps
• B. Increased appetite and weight gain
• C. Fatigue, numbness/tingling, neuropathy, and cognitive changes
• D. Visual disturbances and night blindness

Answer: (C)

Vitamin B12 deficiency shows up mainly with nervous system and hematologic effects because B12 is essential for both DNA synthesis and the formation/maintenance of myelin around nerves. When B12 is low, nerves can become damaged (demyelinated), leading to numbness and tingling and peripheral neuropathy, along with changes in thinking, memory, or mood. Fatigue also occurs, often from the associated macrocytic anemia. This combination—fatigue plus neuropathic symptoms and cognitive changes—is a classic pattern for B12 deficiency.

Other signs listed don’t fit this pattern as well. Shortness of breath can occur with anemia in general, but leg cramps aren’t a typical feature of B12 deficiency. Increased appetite and weight gain aren’t characteristic, and visual disturbances or night blindness point to vitamin A deficiency rather than B12.