DEXA Scan Explained (UK 2026): What It Measures, Private Costs and Radiation Dose

What is a DEXA scan?

DEXA (or DXA) stands for dual-energy X-ray absorptiometry. You lie on an open table while a scanning arm passes over you, using two X-ray beams at different energies. Bone, fat and lean tissue absorb them differently, so the machine can separate them. There is no tunnel, it is painless and usually takes 10 to 20 minutes.

There are two main types:

• Bone density scan of the hip and lower spine, used by the NHS to diagnose or assess the risk of osteoporosis (weak bones prone to breaking).
• Whole-body composition scan, offered privately, showing total and regional fat, lean (muscle) mass, bone mass and an estimate of visceral fat (fat around internal organs). A 2020 review explains how these measurements are made and their limits.

What it claims (privately marketed)

• An accurate body fat percentage, far better than bathroom scales.
• A measure of visceral fat, linked to metabolic and heart disease risk.
• Muscle mass by limb, to track strength training or muscle loss with age.
• Bone density, as an early warning for osteoporosis.

What the evidence shows

How accurate is DEXA for body fat?

DEXA is very repeatable. In a 2026 study of 44 women, the precision error for body fat percentage was about 1.2% for DEXA, similar to good bioelectrical impedance (BIA, the technology in smart scales), and better than 3D body scanners. The key finding was that BIA and 3D scans were not interchangeable with DEXA for individuals, with wide disagreements. So do not compare your DEXA result with a gym scale reading, and always retest on the same machine.

DEXA is not perfect: it assumes standard hydration of lean tissue, and different machine makers give slightly different numbers. Its strength is tracking change in the same person on the same scanner.

How much radiation does a DEXA scan give?

Very little. The International Atomic Energy Agency puts a typical spine plus hip scan at under 1 to about 15 microsieverts depending on the machine, around or below one day of natural background radiation (about 10 microsieverts a day on its figures). For comparison, the UKHSA dose table lists a single chest X-ray at 0.02 millisieverts (20 microsieverts), equivalent to about three days of UK background radiation, with a lifetime additional cancer risk of about 1 in a million. Whole-body composition scans are in a similar low range.

The dose is low enough that occasional scans are reasonable for adults, but it is not zero, so scanning more often than needed is not sensible. DEXA is usually avoided in pregnancy.

Who might reasonably try it?

• People over 50 with osteoporosis risk factors, or younger people with risk factors such as a previous low-impact fracture, long-term steroid use or early menopause. Ask your GP first, as you may qualify for an NHS scan. The NHS uses results alongside a fracture risk assessment.
• People strength training or losing weight who want to know whether they are keeping muscle while losing fat, especially in midlife and later when muscle loss speeds up.
• People who want a visceral fat estimate as part of a wider heart and metabolic risk picture, alongside blood pressure, cholesterol and HbA1c.

Who should be careful?

• Pregnant women, or anyone who might be pregnant, should not have a DEXA scan unless a doctor advises it.
• Anyone prone to body image worries. Detailed fat maps can be upsetting and are not needed for good health.
• People who recently had a barium study or nuclear medicine scan, which can affect results; tell the clinic.
• Frequent scanners. Changes in body composition take time. Retesting more often than every 3 to 6 months mostly measures noise.

How much does a private DEXA scan cost in the UK?

Under UK rules, every medical X-ray exposure must be justified by a qualified professional, so private providers collect health information and arrange a referral for you. Scan.com, for example, states its clinicians send the referral after you book; you do not need to see your GP first.

If you want a scan: what to look for

• Clarity on which scan you are getting: bone density (hip and spine) and body composition (whole body) are different. Some providers offer both.
• The same machine for repeat scans, at a similar time of day, similarly hydrated and before exercise.
• A clear report and explanation, including visceral fat, regional lean mass and, for bone scans, T-scores and Z-scores.
• Professional referral and radiographer-led scanning, which shows the provider follows UK radiation rules.
• Value over hype: you do not need add-ons like metabolic rate estimates, which are calculated rather than measured.

How we chose

This explainer has no product picks. We used NHS guidance, international and UK radiation dose data, and peer-reviewed studies on DEXA precision. Prices come from UK provider pages checked in October 2026.

Bottom line

DEXA is the gold-standard practical way to measure bone density and a precise way to track fat and muscle over time, with a very small radiation dose. If you are over 50 with risk factors, ask your GP about an NHS bone scan first. Privately, a body composition scan from about £125 is worthwhile if you will use it to guide training or weight loss and retest on the same machine after a few months; for most people, waist size, strength and fitness tell you enough.