Why 45kg? The Science Behind Weight Limits

You might feel strong, but if the scale says 44kg, you will be turned away. The minimum weight requirement of 45kg is a non-negotiable safety standard for standard blood donation (350ml bag).

Blood Volume Calculation

A human body has approximately 70-75ml of blood per kg of body weight.

• At 45kg: Total blood volume is ~3.3 liters. Donating 350ml is about 10.5% of total volume, which is safe.
• Below 45kg: Donating the same amount would exceed the safe "13% volume loss" limit, leading to hypovolemic shock, severe dizziness, or fainting.

For 450ml Bags

Some larger bags (450ml) are used for component separation. For these, the donor is usually required to weigh at least 55-60kg.