Food Frequency Questionnaire to Assess Sodium Intake

This study is testing whether a dietary questionnaire (a food frequency questionnaire, or FFQ) can accurately measure how much sodium (salt) people eat, compared to measuring sodium in a 24-hour urine sample. The goal is to find a simpler, non-invasive way to monitor salt intake in patients with high blood pressure or kidney disease. **You may be eligible if...** - You are 18 or older - You have high blood pressure, chronic kidney disease (stages 4–5), or are generally healthy - You are seen in a nephrology or cardiology clinic, or recruited through a clinical investigation center - You have health insurance and are willing to participate fully **You may NOT be eligible if...** - You have conditions causing abnormal salt loss (severe vomiting, diarrhea, or intense sweating within 3 days before urine collection) - Your treatment plan is being changed during the study period - You take certain medications (effervescent drugs, Gaviscon, Tolvaptan, or new/unstable diuretics) around the urine collection day - You are pregnant or breastfeeding - You are protected by special legal status Talk to your doctor to see if this study is right for you.