You don’t drink enough water
Being even slightly dehydrated—as little as 2% of normal fluid loss—takes a toll on energy levels, says Amy Goodson, RD, a dietitian for Texas Health Ben Hogan Sports Medicine. Dehydration causes a reduction in blood volume, explains Goodson, which makes the blood thicker. This requires your heart to pump less efficiently, reducing the speed at which oxygen and nutrients reach your muscles and organs. To calculate your normal fluid needs, take your weight in pounds, divide in half and drink that number of ounces of fluid a day, Goodson recommends. Related: 14 Surprising Causes of Dehydration
