Private Pilot Flight Training and Instruction Flight Training Article Library | Back To 4VFR.COM Dehydration Human need for 2-4 quarts of water a day. You become thirsty with a deficit of 1.5 quarts of body fluids or 2% of body weight. The deficit causes a reduction in blood volume and triggers thirst. Thirst arrives too late and can be mollified too easily. At 3% of body weight fluid loss fatigue and weakness occurs. Symptoms are headache, sleepiness, dizziness and weariness. Avoid diuretics such as coffee and alcohol. Don’t rely on thirst as drinking trigger. Measure fluid intake daily. Written by Gene Whitt Flight Training Article Library | Back To 4VFR.COM