Medicine A patient presents with ascending muscle weakness for 2 days. On examination, the limb is flaccid. What investigation should be done first? A Serum potassium B Serum creatinine C Serum magnesium D Serum calcium 💡 Explanation A patient presents with ascending muscle weakness for 2 days. On examination, the limb is flaccid. What investigation should be done first? ✓ Correct Answer: A. Serum potassium