Real information about blood drawing

Real information about blood drawing

Blood donation & the site preparation

While drawing blood, the site must be prepared for the healthy and safe environment. In general, blood is drawn from the veins (nearest to the skin) of the large arm. The person drawing blood will try to locate the median cubital vein for piercing before drawing blood. The place is inside the elbow.

After locating the right place to pierce, the blood vessel’s upper skin is cleared with chlorhexidine or iodine so that skin bacteria does not contaminate the collected blood nor the donor’s body get infected due to piercing of the skin.

The needle’s size is normally are large, such as 16 to 17 gauge, as it can minimize shearing forces and prevent physical damage of red blood cells, flowing through the needle.   Before starting the blood- drawing procedure, upper arm is wrapped with a tourniquet. This is done to increase the blood pressure in the arm and speeding up the process. The other way of speeding up the blood flow through the vein is giving an object to the donor for squeezing in a repeated way.

A mechanical way of preventing blood clotting

Other than the above said system of blood collection, blood clotting is also prevented through some scientific way.

What is whole blood donation or drawing of whole blood?

Commonly blood is collected from the donor’s body to a medicated container. Depending on the country’s law the amount of blood drawn remains in between 200 milliliters and 550 milliliters. Otherwise of it, 450 to 500 milliliters are the typical measure.

What is the storage unit of collected blood?

A flexible plastic bag is always used for storing collected blood. The bag contains different necessary chemicals like phosphate, dextrose, sodium citrate and sometimes adenine. This is the preventing measure for blood getting clotted as well preserving blood in a good condition. Some other chemicals are also used during the processing the blood.

What is plasma transfusion?

The plasma is separately extracted for transmitting plasma. Fractionation is the known process of medicated plasma transfusion. In fact it is also known as drying of plasma. Some other variants are also used for different types of medications.

What is Apheresis?

Apheresis is a different method of blood donation. In this method, blood is passed through some apparatus. The apparatus not only separates one constituent mainly, it also returns the remaining constituents to the donor. The returnable component in most of the cases is the red blood cells. Because this portion of the blood takes longer time to get replaced. So this method is very helpful for those donors who want to only donate platelets or plasma more frequently than whole blood donation. Even both the plasma and platelet can be donated in place of whole donation.

Like plasma, platelets can be separated from the whole blood, but not through a single donation. It needs multiple donations.

How much amount of blood is required for therapeutic dose?


Any therapeutic dose needs 3 to 10 units of whole blood. In each donation, Platelet apheresis actuates one full dose. The use of Platelet apheresis is to collect source plasma, which is an important item for manufacturing medications (from the whole blood) in the similar system of plasma. If platelet apheresis is collected in the same process of plasma, it is known as concurrent plasma. The use of apheresis is to collect more blood cells, if compared with a single donation, which is called as “double reds. This is mainly for collecting “white blood cells” from blood.

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