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.

People who pee out more salt tend to have higher blood pressure, and this pattern shows up in lots of different groups of people around the world.

For people who already have heart disease, having just the right balance of salt and potassium in their urine — not too much, not too little — seems to be linked to the lowest chance of heart problems or dying from any cause. Too little or too much of this balance is linked to higher risks.

If you have heart disease and eat more salt, your blood pressure tends to go up — for every extra gram of salt you excrete in urine, your top blood pressure number goes up by about 1.3 points and your bottom number by about 0.5 points.

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 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.