Why is blood drawn from the elbow

During a blood draw, a healthcare provider specially trained to collect blood — most likely a phlebotomist or a nurse — inserts a needle into a vein, usually on the inside of your elbow or wrist. As the needle is inserted, it may damage a few capillaries, leading to the formation of a bruise. The person drawing the blood may also insert the needle too far beyond the vein.

If the person drawing blood has any difficulty locating a vein — for example, if your arm is swollen or your veins are less visible — it makes it more likely that blood vessels will be damaged. You might be more prone to bruising during or after a blood draw if you:. Older adults may also bruise more easily as their skin is thinner and has less fat to guard the blood vessels from injury. However, if you notice bruising on other parts of your body or the bruise is very large, you may have another condition that could explain the bruising.

Some people just tend to bruise more easily than others. You should tell your doctor and the person drawing blood if you bruise frequently from having blood taken. If you notice that the person drawing the blood is having a difficult time locating a good vein for a blood draw, you can request the use of another type of needle called a butterfly needle, also known as a winged infusion set or a scalp vein set.

Butterfly needles are often used to draw blood in infants, children, and older adults. A butterfly needle requires a shallower angle and is a shorter-length, making it easier to place in small or fragile veins. If the bruise is large, or you notice that you bruise easily, it could indicate an underlying condition, such as a clotting problem or a blood disease. On top of bruising after a blood draw, you should see your doctor if you:.

Bruises after a blood draw are fairly common and will go away on their own as the body reabsorbs the blood. The bruise is caused by damage to a few small blood vessels during the blood draw process, and is usually not the fault of your healthcare provider.

The bruise may change in color from dark blue-purple, to green, and then brown to light yellow over the course of a week or two before it goes away completely. In this elbow pit, phlebotomists have easy access to the top three vein sites used in phlebotomy:. The median cubital vein, also known as the antecubital vein, is the most common vein for phlebotomy. Located in the antecubital fossa, the median cubital vein is a well anchored, stable vein that rarely rolls during venipuncture.

The median cubital vein is used the most for its accessibility. The median cubital creates less bruising and pain than other draw sites. Within the antecubital fossa, this vein poses the least amount of risk. Unlike the cephalic and basilic veins, the median cubital vein is not near major nerves or arteries. The cephalic vein is a safe secondary option if the median cubital vein is not working. This vein can be found along the upper arm to the thumb, but it is commonly drawn from the forearm or antecubital fossa area.

Also found in the antecubital fossa, the basilic vein serves as a last resort for blood draws. It is not as close to the skin surface as the median cubital and cephalic veins, which poses a greater risk of damage to the median nerve and brachial artery. While the median cubital, cephalic, and basilic veins are the most popular draw sites for blood draws, phlebotomists may resort to other draw sites if their ability to draw is restricted.

The dorsal venous network is the next most common vein site for phlebotomists. If you faint or feel unwell during or after your blood test, you will be asked to stay until you have fully recovered. If you have a tendency to bleed or bruise, let the collector know.

To help prevent bruising to your puncture site, do not carry anything heavy or undertake strenuous exercise within 24 hours of your blood test. When the needle is inserted under the skin you might feel a slight sting and there may be additional discomfort when it is withdrawn. Try drinking water and exercise. Drinking 8 to 10 glasses of liquid a day helps blood flow better and makes the veins more likely to stick up and be found easily, so drink plenty of fluids for a day or two before your test.

You may also want to take a walk while waiting, or on your way to the test, to increase blood flow and keep the veins pumped up routinely doing hand and arm exercises also helps those requiring frequent testing.

Even eating well the day before, if fasting is not required, improves blood flow. Being warm increases your blood circulation, which makes it easier for the phlebotomist to find a vein.

If you have difficulty with blood being taken, lying down and warming your hands under a heating pad and blanket usually provide good results. Difficulty with blood being taken? If you are among those people who have small or difficult-to-access veins, or veins that are scarred or blocked from repeated punctures chemotherapy patients can have this problem you may need to work with the person taking your blood to create a process that works well for you.

If you experience swelling, bruising, or pain then follow putting ice on the site, using the affected arm as little as possible, and taking an over-the-counter painkiller can help.

A blood test is an invasive procedure because a needle is inserted through the skin to reach a vein. It is however a very safe procedure. Millions of blood tests are performed in Australia every year. By far the most common complication is bruising at the site of the needle puncture. This usually appears within 24 hours and may range in size from a small spot to a large purple bruise. It is caused by blood leaking from the punctured vein out into the tissues just under the skin.

This can be reduced by using finger pressure on the site for a minute or so after the blood has been taken. Bruising is more likely if the collection is difficult, if pressure is not maintained on the site for a minute or so, if you are taking anti-clotting medicines such as aspirin or warfarin, if you are an elderly person with fragile veins, or if you exercise your arm soon after the blood test — such as by lifting heavy shopping bags or going to the gym. While bruising is unsightly it is not dangerous and will slowly disappear over a few days or weeks, depending on how extensive it is.

Large bruises may become tender for a few days because the cells that are involved in mopping up the bruise release substances that cause the area to become sore. This is uncommon but again not dangerous. It is part of the healing process. However, if the tenderness is bothering you, you should contact the person or clinic where you had the blood taken.

Very rarely, a small artery, which contains blood at much higher pressure than in veins, will lie unusually close to or underneath a vein.