We have been told by three different doctors (neurologist, cardiologist and ER doctor) to have my daughter increase her fluid and salt intake to help with her lightheadedness and fainting. She was told to drink at least 80 oz of fluids. I had one doctor recommend that taking half your body weight and use that as a guide for how many ounces to drink daily. I believe the goal with the fluids/salt is to increase your overall blood volume. If it is too low, your blood pressure will drop.

When you are going from laying/sitting to standng, you might try moving your legs around and tensing your leg muscles to get the blood moving.