One of the most common preparation questions we hear: exactly how much water, and when? Here's the simple formula.
The Standard Rule
For pelvic and early-pregnancy scans, drink 750ml to 1 litre of water (about 4–6 glasses), finishing 60 minutes before your appointment time. Then don't use the bathroom until your scan is complete.
Why the Timing Matters
Water takes roughly 45–60 minutes to filter through your kidneys and fill your bladder. Drink too late and your bladder won't be full when the sonographer needs it. Drink too early and you'll be in genuine discomfort — or forced to empty it before the scan.
Common Mistakes to Avoid
- Chugging it all at once right before arrival — it won't reach your bladder in time.
- Substituting fizzy drinks — carbonation creates gas that interferes with imaging. Still water is best.
- Overfilling — a painfully distended bladder can compress the structures being examined and make the scan harder, not easier.
- Emptying "just a little" — once you start, it's hard to stop, and a partly empty bladder may not be enough.
What About Other Scans?
Abdominal scans usually require fasting rather than a full bladder, and most other ultrasounds need no fluid prep at all. Always follow the instructions given for your specific scan type.
This article is for general information only and is not a substitute for professional medical advice.
Ready to Book Your Ultrasound Scan?
Mascot Healthcare Clinic, Akoka (Yaba), Lagos offers ultrasound scans by appointment only, Monday–Saturday, 9am–5pm. Book online and choose a time that works for you.