Hello XXXXXXX,

Thanks for your query.

Drinking small sips of water to quench your thirst does not have any harmful effect.
In fact, drinking of plain water is advised before a CT scan to maintain adequate hydration.
Because sometimes CT scans involve injection of a contrast agent, or "dye" to visualize certain structures in the body, to make a better diagnosis.
These contrast agents are filtered by kidneys, and passed out in the urine.
Drinking of small sips of water maintains hydration & reduce any risk of damaging the kidneys.

So, you can have small sips of water to quench your thirst.
But avoid caffeinated drinks & please do not eat solid foods for four hours prior to your CT scan.

Wishing you a good health.
Let me know if I need to clarify further.
Thanks & take care.

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