Final answer:
Furosemide, a diuretic used to treat CHF and hypertension, can mask signs of uncontrolled diabetes by increasing blood glucose levels.
Step-by-step explanation:
The drug used to treat congestive heart failure (CHF) that can mask the signs of uncontrolled diabetes is likely a diuretic, such as Furosemide (Lasix). Diuretics are often prescribed for the management of hypertension and CHF because they help to reduce fluid overload and lower blood pressure. However, diuretics can increase blood glucose levels, which may mask the signs of uncontrolled diabetes. Furosemide works on the loop of Henle and inhibits the reabsorption of sodium (Na+) and chloride (Cl-), leading to diuresis (increased urine production).