People who pee out more potassium tend to have lower blood pressure, at least in adults between 20 and 59—but this isn’t true for everyone everywhere.

People who pee out more salt tend to have higher blood pressure, and their blood pressure tends to rise faster as they get older—but in whole populations, the average blood pressure and how many people have high blood pressure don’t seem to change based on salt levels.

For people with heart disease, the more potassium their body gets rid of in urine, the higher their blood pressure tends to be — every extra gram of potassium excreted per day raises systolic pressure by about 1 point and diastolic by about 0.6 points, which is the opposite of what doctors usually expect.

People in Shanxi Province with high blood pressure who pee out less potassium tend to have higher blood pressure, especially at night—and this pattern is stronger in women than in men.

For people who already have heart disease, the more potassium their body gets rid of in urine, the more likely they are to have a heart attack, stroke, or die — which is the opposite of what most people think potassium does.

When people pee out more salt than potassium, their blood pressure tends to be higher — it’s like the balance between salt and potassium in your urine tells you something about your blood pressure.