Can a person draw 800cc of blood at once

A single blood donation of healthy adults usually does not exceed 400 milliliters, and 800 milliliters far exceeds the safety standard, which may pose serious health risks. The amount of blood donation must strictly follow national regulations, mainly considering factors such as the donor's weight, hemoglobin level, and health status. According to China's Blood Donation Law, the upper limit for a single blood donation is 400 milliliters, and adults weighing over 50 kilograms can donate 300-400 milliliters of whole blood. 800 milliliters is equivalent to 15-20% of the total blood volume in the human body, far exceeding the safe threshold. Excessive blood donation can lead to a sudden drop in blood volume, resulting in symptoms such as dizziness, fatigue, pale complexion, and insufficient circulating blood volume. In severe cases, it can cause hypovolemic shock. Before donating blood, a hemoglobin test is required. Men who consume less than 120 grams per liter and women who consume less than 115 grams per liter are not eligible for blood donation. After donating blood, it is necessary to supplement iron containing foods such as animal liver and spinach, and avoid vigorous exercise within 24 hours. When a large amount of blood collection is required in special medical situations, it must be carried out by a professional medical team under monitoring conditions, equipped with intravenous fluid replacement and vital sign monitoring equipment. In special circumstances such as autologous blood transfusion surgery, blood collection of 800 milliliters should be completed in batches, with an interval of no less than 72 hours between each session, and preoperative evaluation of cardiovascular and pulmonary function is required. After blood collection, it is necessary to immediately supplement crystalloid fluid to maintain stable circulation. If hemoglobin is below 70 grams per liter, blood transfusion treatment should be considered.

It is recommended to follow the guidance of a regular blood station when donating blood. After donating blood, press the needle hole for more than 10 minutes and do not remove the dressing within 4 hours. Keep the puncture site clean and dry for 24 hours to avoid infection. If discomfort symptoms such as palpitations and sweating occur, immediately lie down, drink sugary drinks, and contact medical staff. Regular blood donors should ensure a weekly intake of 40-75 grams of red meat, combined with vitamin C to promote iron absorption. The interval between two blood donations should not be less than 6 months.