Final answer:
The health care professional should suspect lactic acidosis as the adverse reaction to Metformin (Glucophage) when a patient reports muscle pain.
Step-by-step explanation:
The health care professional should suspect lactic acidosis as the adverse reaction to Metformin (Glucophage) when a patient reports muscle pain. Lactic acidosis occurs when there is an excessive production of lactic acid in the body. Metformin can sometimes cause lactic acid to build up, leading to symptoms such as muscle pain, weakness, and fatigue.