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It is normal to sometimes bruise after a blood draw. This can happen for different reasons, such as liver problems, certain medicines, and a lack of vitamins. Some people bruise more easily than others.

It mostly goes away on its own without treatment. However, if the bruise is large and accompanied by bleeding elsewhere in the body, it indicates a serious problem.

How Blood Is Drawn?

If your doctor needs a blood sample, a doctor, nurse, or phlebotomist (a person trained to draw blood) will take it. First, they put a tight band around your upper arm to make your veins easier to see. Then, they clean the inside of your elbow.

Next, they insert a small needle into your arm to collect blood in small bottles. After they remove the needle, they press a gauze or cotton ball on the spot to stop the bleeding. They might ask you to press on it, too, and then they put a bandage on it.

Why Does Bruising Happen?

Bruising after a blood draw can happen for several reasons. Knowing these reasons can help reduce bruising. The following are common causes of bruising after a blood draw:

Needle Position

When drawing blood, the nurse usually inserts the needle at a specific angle (about 15°) to enter the vein correctly. After piercing the skin, the needle moves deeper under the skin before reaching the vein. This means there are two needle points—one in the skin and one in the vein.

If pressure is only applied to the skin’s surface and not the vein, the puncture in the vein might keep bleeding under the skin, causing a bruise or even a larger blood collection called a hematoma.

Not Enough Pressure

Another common reason for bruising is not applying enough pressure to the puncture site. If pressure is released too soon, the puncture might not close completely. Therefore, more bleeding and bruising occur.

Moving the Needle Site

Rubbing the area where the needle was inserted or moving the cotton ball around can interrupt the clotting process. This can cause the blood vessels to start bleeding again, triggering a bruise under the skin.

Lack of Observation

Not checking the puncture site while applying pressure can slow down the clotting process, making bruising more likely. Keeping an eye on the site helps ensure bleeding stops properly and quickly.

Physical Activity

Doing heavy physical activities, like lifting weights, right after getting your blood drawn can interfere with the healing of the blood vessels. This can cause more bleeding and lead to bruising.

When Should I Be Worried About Bruising After a Blood Test?

Most of the bruises heal in 1-2 weeks with some preventive measures. Bruising after blood draw treatment includes conservative approaches. However, you must seek medical help if:

  • The swelling gets much worse.
  • Your hand changes color or feels numb.
  • You have throbbing or intense pain.

Wrapping Up

Blood tests are common to rule out many things inside our bodies. Therefore, the formation of a bruise after a blood draw is normal. You can reduce the chances of bruising by using proper pressure techniques, keeping an eye on the puncture site, and avoiding strenuous activities after a blood draw.

In case the bruising worsens, visit Dr. Muhammad Irfan at the Family Diagnostic Clinic. Our doctor is board-certified in internal and palliative medicine and treats various common and complex issues. Call us at (281) 351-6800 to book an appointment.

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