Drowsiness after blood draw is usually caused by a vasovagal reaction.
Adverse reactions with predominantly systemic manifestations, i.e., vasovagal reactions, may occur after blood draws, with triggers including psychophysiologic factors in the donor as well as decreased blood volume.
Most of the symptoms are mild, manifesting as generalized discomfort, weakness, pallor, sweating, anxiety, dizziness, and nausea. A few are more severe and may include transient loss of consciousness (syncope), convulsions, or incontinence. If fainting and falling occur, it can lead to accidental injury.
Therefore, it is recommended to rest appropriately after blood sampling, avoid prolonged and heavy activities, and eat a small amount of food such as candies and chocolates to replenish energy. If there is still more serious drowsiness after resting and eating, it is recommended to go to the hospital for examination and improve the symptoms with doctor’s advice if necessary.
It is important to be aware of whether there is a combination of diseases such as anemia. If there is a combination of anemia, it is recommended to eat more iron-rich foods (e.g., animal offal, spinach, etc.) to help replenish the body’s needs. If drowsiness is severe or persists after blood sampling, go to the hospital for a positive diagnosis.