Answer
They help check kidney function and electrolytes such as potassium and sodium, which can change during treatment or illness.
Sources for this answer
- Losartan Potassium and Hydrochlorothiazide 100/12.5mg tablets — Current selected SmPCemc · Summary of Product Characteristics
- NHSNHS · NHS medicine guidance
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.