How to Prepare for Your Ultrasound Scan
Scan-specific preparation instructions from our consultant sonographers — fasting rules, bladder preparation, what to wear, and what to bring. Covers every scan type we offer.
- Scan-specific instructions
- Written by consultant sonographers
- Updated July 2026
Does Preparation Matter for an Ultrasound Scan?
Preparation matters for some ultrasound scans and is entirely unnecessary for others. Whether you need to fast, fill your bladder, or simply arrive in comfortable clothing depends entirely on which scan you are having. Arriving unprepared for a scan that requires preparation may mean the scan cannot be completed — or that findings are obscured and a repeat appointment is needed.
This guide gives you the specific instructions for every scan type we offer at Sonoworld. If you are unsure which preparation applies to your booking, your confirmation email will include the relevant instructions, or you can call us on 020 3633 4902.
For a full explanation of what happens during your appointment, see our guide: What Is an Ultrasound Scan?
Abdominal Ultrasound Scan — Preparation Required
Abdominal scans assess the liver, gallbladder, pancreas, spleen, and kidneys. The gallbladder is the primary reason fasting is required: it stores bile and expands when empty. When you eat — particularly fatty food — the gallbladder contracts to release bile into the bowel, making it difficult to visualise on ultrasound.
Fasting Instructions
- Fast for 4 hours before your appointment. Do not eat any food during this period.
- Water is fine — you may drink plain water freely. Staying hydrated helps image quality.
- Black coffee or black tea (no milk) is acceptable in small amounts.
- Avoid fizzy drinks — carbonated beverages increase abdominal gas, which can obscure structures.
- Take your regular medications with a small amount of water unless your doctor has advised otherwise.
What If I Only Need My Liver Checked?
If your scan is specifically to assess the liver — for example, to investigate fatty liver or cirrhosis — fasting is less critical because the liver is visible regardless of gallbladder state. However, if there is any possibility your gallbladder will be assessed, fasting is always recommended. When in doubt, fast for 4 hours.
For abdominal scan booking, see: Women's Abdominal & Pelvic Scan | Men's Abdominal & Urinary Tract Scan
Pelvic Ultrasound Scan — Full Bladder Required
For a transabdominal pelvic scan, you must arrive with a full bladder. The bladder sits in front of the uterus and ovaries, and when full it acts as an acoustic window — pushing the bowel out of the way and allowing clear visualisation of the pelvic organs beneath it.
Bladder Preparation Instructions
- Drink 1 litre (approximately 4 large glasses) of water in the hour before your appointment.
- Do not empty your bladder from the time you start drinking until after the scan.
- If you need to urinate urgently before the scan, tell your practitioner — they can advise whether to partially empty and refill.
Pelvic scan booking: Book Pelvic Ultrasound Scan
Transvaginal Ultrasound — Minimal Preparation
A transvaginal scan uses an internal probe inserted into the vagina to obtain higher-resolution images of the uterus and ovaries. Because the probe is positioned close to the pelvic organs, a full bladder is not required — in fact, an empty or partially filled bladder is preferred.
- You do not need to fast.
- You do not need a full bladder — empty your bladder before the scan if comfortable to do so.
- Wear comfortable, easily removable clothing.
- The probe is covered with a sterile sheath and gel before insertion. The procedure is similar to a cervical smear in terms of positioning.
For more information, see our dedicated guide: Transvaginal Ultrasound: Pain, Cramping & What to Expect
Early Pregnancy Scan — Full Bladder (Before 10 Weeks)
For early pregnancy scans before approximately 10 weeks, a full bladder is required for the same reason as a pelvic scan — it provides the acoustic window needed to visualise the uterus. After 10 weeks, the uterus is large enough to be seen without a full bladder, and a transvaginal approach may be used for earlier gestations.
- Drink 1 litre of water in the hour before your appointment.
- Do not empty your bladder before the scan.
- If a transvaginal scan is needed for a clearer image, your practitioner will explain this beforehand and obtain your consent.
Pregnancy scan booking: Pregnancy Appointments
MSK (Musculoskeletal) Scans — No Preparation Required
Musculoskeletal scans assess tendons, ligaments, muscles, and joints. No fasting or bladder preparation is required. The only practical consideration is clothing.
- Shoulder scan: Wear or bring a vest top or sleeveless shirt for easy access to the shoulder.
- Knee or ankle scan: Wear or bring shorts, or loose trousers that roll above the knee.
- Hip scan: Wear loose trousers or a skirt that allows access to the hip area.
- Elbow, wrist, or hand scan: No special clothing needed — a short-sleeved top is helpful.
MSK scan booking: MSK Appointments
Vascular Scans — No Preparation Required
Vascular scans — including carotid Doppler, DVT scan, echocardiogram, and AAA screening — do not require fasting or bladder preparation.
- Carotid scan: Wear a low-collar top or shirt that can be opened at the neck.
- DVT scan (leg): Wear or bring shorts, or loose trousers that roll above the knee.
- Echocardiogram: Wear a top that can be easily removed or opened at the front — electrodes will be placed on your chest.
- AAA screening: No special preparation — wear comfortable clothing.
Vascular scan booking: Vascular Appointments
Breast, Thyroid, and Neck Scans — No Preparation Required
No fasting or bladder preparation is required for breast, thyroid, or neck scans.
- Breast scan: Wear a two-piece outfit — a top that can be removed easily. Avoid wearing a one-piece dress.
- Thyroid or neck scan: Wear a low-collar top or shirt that can be opened at the neck. Avoid necklaces or scarves.
Breast scan booking: Book Breast Ultrasound Scan | Thyroid scan booking: Book Thyroid & Neck Scan
From Our Practice
The most common preparation error we encounter is patients who drink water before a pelvic scan but do not hold it — they empty their bladder on arrival, assuming the water they drank was sufficient. By the time they are on the examination couch, the bladder is empty and the bowel has moved back into the pelvic cavity, obscuring the uterus and ovaries.
When this happens, we have two options: wait 20–30 minutes for the bladder to refill, or convert to a transvaginal approach (with the patient's consent). Both are manageable, but both add time to the appointment and can cause unnecessary anxiety. The fix is simple: drink your water in the hour before arrival, and do not use the toilet from that point until after the scan.
The second most common issue is patients who fast for 8 hours or more before an abdominal scan because they found that instruction online. Prolonged fasting is unnecessary and uncomfortable. Four hours is sufficient for gallbladder filling in the vast majority of patients.
Observations above are drawn from composite patterns across our patient population, not from any individual case. Always follow the specific instructions in your booking confirmation, and contact us if you have any questions about preparation for your particular scan.
Preparation at a Glance
| Scan Type | Fast? | Full Bladder? | Clothing Note |
|---|---|---|---|
| Abdominal (liver, gallbladder, kidneys) | Yes — 4 hours | No | Comfortable, loose top |
| Pelvic (uterus, ovaries) | No | Yes — 1 litre, 1 hour before | Two-piece outfit |
| Abdominal & Pelvic combined | Yes — 4 hours | Yes — 1 litre, 1 hour before | Two-piece outfit |
| Transvaginal | No | No — empty bladder preferred | Easily removable lower clothing |
| Early pregnancy (<10 weeks) | No | Yes — 1 litre, 1 hour before | Two-piece outfit |
| Breast | No | No | Two-piece outfit |
| Thyroid / neck | No | No | Low-collar top; no necklaces |
| MSK (shoulder, knee, hip, etc.) | No | No | Loose clothing for access |
| Vascular (carotid, DVT, echo, AAA) | No | No | Low-collar or front-opening top |
| Testicular | No | No | Comfortable, easily removable lower clothing |
Preparation FAQs
Can I eat before an abdominal ultrasound scan?
No — you should fast for 4 hours before an abdominal scan. This allows the gallbladder to fill with bile and become visible on ultrasound. You may drink plain water freely during the fasting period. Always seek individual professional advice if you have a medical condition that affects fasting.
Can I drink coffee before an ultrasound scan?
Black coffee or black tea (no milk) is acceptable in small amounts before an abdominal scan. Avoid fizzy drinks, which increase abdominal gas. For scans that do not require fasting, there are no dietary restrictions.
How full does my bladder need to be for a pelvic scan?
Drink 1 litre (approximately 4 large glasses) of water in the hour before your appointment, and do not empty your bladder from that point until after the scan. A comfortably full bladder — not uncomfortably distended — is the target. If you are in significant discomfort on arrival, tell your practitioner.
What should I wear to my ultrasound scan?
Wear comfortable, loose-fitting clothing that allows easy access to the area being scanned. For abdominal or pelvic scans, a two-piece outfit is ideal. For MSK scans of the knee or ankle, shorts are helpful. For thyroid or carotid scans, a low-collar top is best. Avoid wearing jewellery near the scan area.
Can I take my medication before an ultrasound scan?
Yes — take your regular medications as normal with a small amount of water, unless your doctor has specifically advised otherwise. If you are on anticoagulants or other medications that may affect a procedure (such as an injection), please mention this when booking. Always seek individual professional advice about your specific medications.
What happens if I arrive unprepared for my scan?
For scans that require fasting or a full bladder, arriving unprepared may mean the scan cannot be completed or that image quality is compromised. In most cases, we can accommodate a short wait to allow the bladder to refill. If you have fasted for less than 4 hours before an abdominal scan, please call us before your appointment — we can advise whether to proceed or reschedule.
Sources
- Society of Radiographers & BMUS. Guidelines for Professional Ultrasound Practice. 2021. Accessed July 2026. bmus.org
- Sondh RS et al. Reducing prolonged fasting for abdominal ultrasound scans. BMJ Open Quality, 2023. doi:10.1136/bmjoq-2023-002269
- Sonoworld clinical imaging team. Composite practice patterns — Sonoworld Diagnostic Services, Marylebone, London. July 2026.
Ready to Book?
Same-day and next-day appointments available. Your booking confirmation will include scan-specific preparation instructions.
29 Weymouth Street, Marylebone, London W1G 7DB
