Is donating blood harmful to health?

There are many rumors that donating blood is harmful to your health. An article that has been circulating on the Internet for a long time has listed several aspects in detail, claiming that donating blood is harmful to the body. But are these claims reliable in the eyes of medical professionals? Let's see how a medical doctor and senior editor of a health magazine refutes these rumors.

Rumor: Donating blood will cause the weakening or even loss of blood function. The decrease in red blood cells will cause various organs in the body to not get enough oxygen, and the various life functions of the cells cannot function normally. The dizziness after donating blood is because the brain does not get enough oxygen. A decrease in white blood cells will reduce the body's ability to resist viruses, making it more susceptible to illness. This is the reason why people feel weak after donating blood. The decline in immunity gives the originally insignificant cold virus an opportunity to take advantage. A decrease in platelets can make wound healing difficult. The main cause of leukemia is thrombocytopenia. Maybe you will say, everyone says that the body will produce enough blood after donating blood, but you know that all blood cells are differentiated from hematopoietic stem cells in the bone marrow. Hematopoietic stem cells have a lifespan. The book says that the blood volume will be fully replenished 2 weeks after donating blood. But please note: what is being supplemented? It is plasma. Blood and plasma are two different concepts. You will feel thirsty after donating blood, which means you need to replenish plasma. This is why blood stations provide sugar water or milk free of charge.

The truth: This myth contains many misunderstandings about the physiological process of recovery after donating blood. We explain the rumors one by one.

Is the amount of donated blood a lot compared to the total amount of blood in the body?

Usually 200 ml of blood is donated at a time. Precious blood (such as AB type blood. Note: It is not necessarily RH negative blood, because RH negative blood is too rare. The "alliance" method is often adopted. As long as you join the "alliance", when you need blood, other "allies" will go to the blood station to donate blood designated for the ally.) may require 400 ml. The interval between two collections should be no less than 6 weeks (many other countries stipulate that it is 12 weeks). 200 milliliters is 0.2 liters, and the total blood volume of an adult is about 4.2-4.8 liters. The amount of donated blood only accounts for about 5% of the total blood in the body. It is not a large number for a healthy person and will not cause any harm to the body. Women bleed 30 to 50 ml during "those days" every month, and this happens every month. Some women bleed up to 80 ml. Adding up all the blood over 6 months is more than 200 ml. And yet they still eat, travel, and some people still drink, exercise, and have sex as usual. By comparison, it can be seen that the small amount of blood donated is not a big loss to the whole body.

Why do I feel dizzy and nauseous after donating blood?

Some people who donate blood for the first time are prone to dizziness and nausea, which is usually due to changes in blood pressure combined with emotional stress. Smoking and drinking can also aggravate dizziness. Blood pressure is the pressure of blood against your blood vessels. Imagine you are blowing air into a rubber tube. The harder you blow, the greater the pressure on the tube wall. Blowing air into the tube with your mouth is like the heart pumping blood into the blood vessels throughout the body. High blood pressure is often caused by hard blood vessel walls with poor elasticity, while low blood pressure may be caused by insufficient force in the heart to pump blood, a slow heart rate, or low blood volume (people who are injured and bleeding may have such low blood pressure that it cannot be measured). But this change in blood pressure will be quickly adjusted by the body. If you always have low blood pressure after donating blood, then patients with hypertension don't need to take medicine and should just have bloodletting; there will be no such disease as "congestive heart failure" (peripheral blood pressure is too high and the heart can't pump). After donating blood, you often need to rest for a while and eat and drink something. When you get up the next day, move gently to allow your blood pressure to adjust. Avoid delicate labor when you feel uncomfortable. It's not a problem as long as you eat enough and drink enough, especially drink enough and don't let yourself become dehydrated.

Is it easy to get sick after donating blood?

White blood cells are indeed related to immunity, but they are not the only factor that determines immunity. Just like if your bonus of 200 yuan was deducted this month, it doesn’t mean that your family is poor. On the other hand, women will have a slight increase in white blood cells during menstruation, but there is no such phenomenon that "women are less likely to get sick during menstruation." Conversely, some literature suggests that older or postmenopausal donors can get rid of excess iron in their bodies, which is associated with heart attacks - but the literature also notes that while this phenomenon has been observed, the association needs further confirmation.

Is thrombocytopenia caused by blood donation related to leukemia?

Rumor says: "The main cause of leukemia is thrombocytopenia." In fact, what people generally call "leukemia" is clinically a type of blood disease. As long as the proportions of various components in the blood are unbalanced, it may cause the blood system to malfunction, which is called "disease." Their causes are unrelated, and even " leukocytosis" is not their only manifestation. Even when it comes to "leukemia" in a narrow sense that is mainly related to white blood cells, "thrombocytopenia" is only one of the manifestations, not its cause or inducement. And the recovery of platelets is not difficult. The textbook says: The lifespan of platelets is 7-10 days, and aging platelets are cleared by the mononuclear macrophage system. Platelets are different from granulocytes in that they are not stored in the bone marrow. If a large number of platelets are destroyed, their recovery will be slow, and it will take at least 3-5 days for them to return to normal. This is exactly the time required for megakaryocytes to mature and produce platelets. That is to say, if you lose 5% of your platelets, even if that is considered a "large amount", it will only be restored in a few days. So what about other components in the blood? Water and inorganic salts are replenished in 2 hours; most other substances are almost replenished in 2 days. The slowest to recover are red blood cells, because their lifespan is 100-120 days. When they are significantly lost, the bone marrow will produce blood at 6 to 8 times the speed, and recovery will not exceed 1 month. Therefore, the rumor that "the blood volume will be fully replenished 2 weeks after donating blood" does not describe the correct situation.

Who can't donate blood?

Simply put, blood donation is not allowed when there is a risk to the blood donor or the blood user.

Specifically include: those who have donated blood recently (China stipulates 6 months); those who are underweight or overweight; those who are anemic; those who suffer from various infectious diseases or are at risk of infectious diseases (for example, the UK stipulates that people who have had male sexual intercourse within 12 months or have had tattoos within 4 months are not allowed to donate blood; Singapore stipulates that people who have lived in the UK or France for a certain period of time are not allowed to donate blood - because of mad cow disease CJD); those who have malignant tumors or a history of illness; those who have serious chronic diseases or autoimmune diseases...etc. In addition, breastfeeding mothers generally do not donate blood, especially within 6 months after giving birth. This may reduce your body's iron stores and put your baby at risk of iron deficiency.

How to supplement iron after donating blood?

Food supplements. It should be noted here that although many foods are rich in iron, the iron in vegetables (including Popeye's spinach), beans, cereals, seaweed, eggs, cheese, and shellfish is non-hemoglobin iron, which is not easily absorbed. Iron supplementation still needs to come from animal liver, whole blood, fish and livestock and poultry meat.

How to rest after donating blood?

Do not engage in heavy physical labor or strenuous exercise on that day. Drink more water than usual, 4 large glasses of 250 ml each. Note that it is water, not coffee or alcohol. Avoid excessive heat. What should be avoided are: dieting, lack of water, smoking, standing for long periods of time...these will affect your recovery.