Which of the following is a common side effect of lithium?

• A. Hair loss
• B. Hypertension
• C. Diarrhea
• D. Tremor

Answer: (D)

Tremor is a very common side effect of lithium, especially when starting treatment or after increasing the dose. The usual presentation is a fine tremor of the hands that patients notice early on. This effect is dose-related, which is why adjusting the lithium dose or, if needed, adding a small dose of a beta-blocker like propranolol can help manage it.

Other options aren’t as typically seen with lithium. Hair loss isn’t a standard or frequent reaction, and hypertension isn’t commonly linked to lithium therapy. Diarrhea can occur, but it’s less characteristic and not as consistently reported as tremor. The prominence and frequency of tremor make it the best-supported answer for a common adverse effect.