If your body retains too much fluid (volume overload), your blood pressure can be difficult to control. One cause is consuming too much sodium. Cutting back may help. Kidney disease may also be the culprit. You may need to take a medication called a loop diuretic.
How do you know if you're retaining fluid? Thoracic bioimpedence is one technique to check for volume overload. This technique uses a small, painless electric current to determine how hard your heart is working, the level of resistance in your arteries and the amount of fluid in your body.