At some time in life, every person will do a blood test, and not only one but multiple as life goes on. Blood tests are common and every day millions of blood tests are done around the world.
Blood donation, which is similar to blood tests in many ways, is also common around the world, but not every one will do a blood donation.
Blood donation is not mandatory, it is up to a person if they want to donate blood, however, while a blood test is not forced upon any one, doing a blood test is needed to find out about your health or to diagnose a disease.
So, what is the difference between a blood test and a blood donation? A blood test is when a phlebotomist draws a small amount of blood from a vein in your arm and sends it to the lab for testing. Blood donation is when a person donates a pint of blood to the blood bank, which is used for blood transfusion purposes.
What are Some Differences Between the Two?
A blood donation is similar to a blood test in many ways. The same tools used when drawing blood for a blood test are the same ones used when donating blood except that the needle gauge for blood donation is an 18 gauge while for a blood test it is either a 21, 22, or 23 gauge.
Also, a combination of 70% isopropyl alcohol and povidone iodine solution is used when preparing the site for needle insertion in blood donation while with a blood test only alcohol is used.
The needle stays in the vein for a much longer time during blood donation than for a blood test. Donating a pint of blood can take anywhere from 6 to 10 minutes depending on how fast the person blood is flowing. That means that the needle will be in your vein for that amount of time. For a blood test, you can expect the needle to be in your vein for under a minute, in most cases.
Can a Blood Test Make You Tired?
A blood test in itself will not make you tired because the amount of blood drawn is a small amount. Even if you had 5 vials of blood drawn from your vein, it is still a small amount of blood compared to a blood donation.
Let me give you a visual of how much the amount of blood for a blood test looks like. Think of a teaspoon. 1 teaspoon is about 5 ml of blood. A CBC tube vial is 4 ml. If a technician drew 5 CBC tubes of blood from you, that would be about 5 teaspoons or 1 tablespoon and a half (a little over half).
While 5 teaspoons may sound like a lot, the amount of blood that is drawn from you is not. For that reason, a blood test should not make you tired in itself. However, there are other things that can cause it. Read How Much Blood is Drawn for a Blood Test.
Here are several things that can cause you to feel tired after a blood test.
Anxiety or stress: Not every one is cool about doing a blood test. Fear of blood, needles, and the thought of the whole process can cause some people to feel anxious or stressed about the blood test, which in turn can trigger a release of stress hormones and lead to feelings of fatigue or exhaustion.
Fasting: If you were instructed to fast before your blood test, that is, avoid eating or drinking anything except water for a certain period of time, that can lower your blood sugar levels and contribute to feelings of tiredness or weakness.
Dehydration: If you did not drink enough water before the blood test, you may become dehydrated, which can cause fatigue.
Iron deficiency: If you have an iron deficiency you may already be tired before the blood test. So, it’s not the blood test that is making you feel tired.
Underlying medical conditions: In some cases, if you feel tired after a blood test it may be a symptom that you have an underlying medical condition, such as anemia, thyroid disease, or infection. If your tiredness persists for some time or it is accompanied by other symptoms, it may be a good idea for you to talk with your healthcare provider about how you are feeling and rule out any underlying issues.
What about blood donation? Blood donation can make you feel tired. When you donate blood you are donating 1 pint, which is about 473 ml or using the visual above, 95 teaspoons or 32 tablespoons. That is a lot of blood. So, it is very possible to feel tired after donating a pint of blood.
However, not every one will experience tiredness after blood donation. Some people experience it while others don’t. When you donate a pint of blood, you lose a significant amount of fluid which can cause your blood volume to temporarily decrease. That can cause 3 things to happen:
1. It can temporarily lower your blood pressure making you feel a bit tired. Your body now has less blood and your heart has to work harder to pump blood around your body to maintain the body’s equilibrium.
2. It can cause a temporary decrease in the number of red blood cells in your body, which can temporarily reduce hemoglobin causing you to feel a bit tired. Red blood cells are responsible for carrying oxygen to your body’s tissues. If your body has fewer red blood cells, it can be harder for your body to get the oxygen it needs, which can leave you feeling tired.
3. It can lead to dehydration which can cause tiredness. As dehydration occurs, your blood pressure will drop, leading to poor circulation and reduced blood flow to your brain, which leads to tiredness. To prevent dehydration and counter tiredness, drink plenty of fluids before and after donating blood.
Can a Blood Test Make Your Arm Ache?
It is possible for your arm to hurt or ache after having your blood drawn. When the needle pierces the skin you can feel some pain and after the needle has been removed from the vein, you can also feel pain due to bruises made during venipuncture.
There is also the possibility of hitting a nerve in your arm, which could cause your arm to ache for awhile. This is rare, but it can happen. Also, if you move your arm while the needle is in the vein, bruising can happen.
However, if a blood draw is done properly, feeling hurt or pain should be minimized.
What about blood donation? The same things can happen during blood donation. However, blood donation is a longer procedure, which means that the needle stays longer in the vein than during blood draw and the needle gauge is bigger. As a result, more bruising can occur leaving your arm aching you more.
Notwithstanding, if the needle insertion is done properly and the rest of the procedure goes well, the side effects can be minimized.
Can a Blood Test Make You Dizzy?
The amount of blood drawn for most test is not a lot, so you should not feel dizzy after a blood test. If you have been fasting and you are hungry, then it’s likely a drop in your sugar levels could cause some dizziness.
Also, if you are dehydrated you could be feeling dizzy before and after the blood test. However, it is not necessarily due to the blood that was drawn from you.
Many people experience dizziness but more often than not it is likely due to a vasovagal reaction coming from your nervous system. It can be triggered by seeing the needle, seeing your own blood, or just being anxious about the whole thing.
Most times the reason for feeling dizzy is due to this physical response from your nervous system.
Other than you being hungry, dehydrated, or having an underlying condition, your dizziness is due to the stress and anxiety brought on by the venipuncture process, not the amount of blood drawn.
What about blood donation? The amount of blood drawn for donation is quite a lot and therefore is possible to make you feel dizzy. Donating a pint of blood can cause your pressure to temporarily drop, dehydration, and a temporary drop in your hemoglobin.
Add to that if you didn’t drink a lot of fluids before donation or if your hemoglobin is on the lower end of the normal range.
Add to that also if you have fear of blood and needles. So, there are several factors that can bring about dizziness during or after blood donation.
The symptoms that you experience, though, are only temporary really and should go away within a few hours or days. If symptoms are lasting longer, then you should probably see your healthcare provider and get some advice or intervention.
Can a Blood Test Make You Feel Weak?
Some people experience weakness during or after a blood test but it’s most likely due to a vasovagal reaction that they are having. The amount of blood drawn is usually a small amount and should not cause weakness.
Can a Blood Test Make You Pass Out?
It is possible for a person to pass out or faint during or after a blood draw. However, it is very unlikely that it was because of the amount of blood that was drawn. Most likely, stress and anxiety brought on by the procedure is the culprit.
Key Takeaways
The amount of blood drawn is not enough to cause you to be tired, dizzy, feel weak, or pass out. However, a fear of needles, blood, or the phlebotomy procedure can cause these symptoms to show up.
The amount of blood donated can cause you to be tired, dizzy, feel weak, or maybe even pass out. Fear, too, of needles, blood, or the whole thing can bring about that.