Preparing for a FibroScan is straightforward: fast for at least two hours beforehand, wear a top you can easily lift, and avoid alcohol before your appointment. The test itself takes about 10 minutes, requires no sedation, and is completely painless. But a few small details in your preparation can make the difference between accurate results and a reading your doctor can’t trust.
Fasting Before the Scan
You should avoid eating for at least two hours before your FibroScan. Some clinics ask for three hours, so follow whatever your specific provider tells you. Eating raises blood flow to your liver, which temporarily increases liver stiffness and can inflate your results. Water is generally fine during the fasting window, but check with your clinic if you’re unsure.
Alcohol is also off limits before the scan. The NHS advises not drinking alcohol before your appointment, and many clinics recommend abstaining for at least 24 hours. Alcohol causes short-term inflammation in the liver that can make stiffness readings appear worse than they actually are.
What to Wear
The technician needs direct access to the right side of your abdomen, between your ribs and hip. You won’t need to remove your clothing entirely, but you will need to lift or pull aside whatever you’re wearing on your upper body. A loose-fitting top that pulls up easily is ideal. Massachusetts General Hospital specifically recommends that women avoid wearing a dress, since it’s harder to expose just the right side of the torso.
You don’t need to change into a gown. Comfortable pants or a skirt paired with a separate top is the simplest approach.
Medications and Supplements
Most clinics do not require you to stop your regular medications before a FibroScan. It’s a non-invasive imaging test, not a blood draw or surgical procedure, so there are typically no drug interactions to worry about. That said, if your provider gave you specific instructions about holding any medications, follow those. Bring a list of what you take so the technician or doctor reviewing your results has context.
What Happens During the Test
You’ll lie on your back with your right arm raised above your head to open up the space between your ribs. The technician places a probe (similar to an ultrasound wand) against the skin over your liver area, on your right side. A small amount of gel goes on the skin first, just like a regular ultrasound.
The probe sends painless vibration waves through your liver. You’ll feel a gentle “flick” sensation each time a pulse is generated. The technician takes multiple readings, usually around 10, and the whole process is over in about 10 minutes. There’s no recovery time, no sedation, and no restrictions on driving or eating afterward.
Factors That Can Affect Your Results
A FibroScan measures two things: liver stiffness (which correlates with scarring or fibrosis) and fat content. Both readings can be thrown off by factors that have nothing to do with your actual liver health.
Eating too recently is the most common and most preventable issue. Beyond that, body composition plays a significant role in whether the scan produces reliable readings at all. Research shows that in people with a BMI of 30 or higher, nearly half of scans produce failed or unreliable measurements. A BMI above 27.7 nearly triples the odds of an unreliable result compared to leaner patients. This doesn’t mean the test can’t work if you carry extra weight. Clinics often have a larger probe (called the XL probe) designed specifically for larger body types, which improves accuracy considerably. If you know your BMI is on the higher side, it’s worth confirming ahead of time that your clinic has this option available.
Active liver inflammation from any cause, whether a recent flare of hepatitis, heavy drinking in the days before, or even a bad viral illness, can temporarily spike stiffness readings. If you’ve been unwell or had a significant change in your health recently, mention it to your provider so they can factor that into interpreting your results.
Understanding Your Results
The scan produces two scores. The first is liver stiffness, measured in kilopascals (kPa). Normal results typically fall between 2 and 7 kPa. Higher numbers suggest increasing degrees of fibrosis or scarring, with readings above 12 to 14 kPa often pointing toward significant scarring depending on the underlying liver condition.
The second score is the CAP (controlled attenuation parameter), which measures fat in the liver. It’s reported in decibels per meter (dB/m). A CAP score below 238 dB/m is considered normal, meaning the amount of fat in your liver isn’t elevated. Scores above that threshold indicate varying degrees of fatty liver disease, with higher numbers reflecting more fat.
Your doctor will interpret both numbers together, in the context of your medical history, blood work, and the reason the scan was ordered. A single FibroScan is a snapshot. If your results are borderline or unexpected, your provider may recommend repeating the test or ordering additional imaging.
Pregnancy and Implanted Devices
FibroScan is not strictly contraindicated during pregnancy or for people with active implanted devices like pacemakers. The FDA removed those as formal contraindications but noted that extensive studies in these populations haven’t been conducted. If you’re pregnant or have an implanted medical device, let your provider know before the scan so they can weigh the benefits against the limited safety data.