NHS England's DM01 data shows around 1 in 4 people waiting six weeks or more for one of 15 key diagnostic tests (January 2026). The operational standard is that fewer than 1% should wait that long. Because scans and scopes gate almost every treatment decision, diagnostic delays lengthen the whole RTT pathway.
- ✓Around 1 in 4 people wait 6+ weeks for a diagnostic test (DM01, Jan 2026).
- ✓The standard says fewer than 1% should wait six weeks.
- ✓Diagnostic delays sit inside RTT waits — they lengthen everything downstream.
What DM01 measures — and the 15 tests
DM01 is NHS England's monthly count of people waiting for one of 15 key diagnostic tests and procedures. It sits alongside the better-known RTT waiting list but measures something different: not referral-to-treatment, just the queue for the test itself. The 15 tests fall into three broad groups:
- Imaging. MRI, CT, non-obstetric ultrasound, barium enema and DEXA (bone density) scans.
- Physiological measurement. Echocardiography, electrophysiology, peripheral neurophysiology, sleep studies, urodynamics and audiology assessments.
- Endoscopy. Gastroscopy, colonoscopy, flexi sigmoidoscopy and cystoscopy.
The operational standard is demanding: fewer than 1% of patients should wait six weeks or more from referral for a test. As of the January 2026 data, roughly 1 in 4 do.
Why diagnostics bottleneck everything downstream
Almost no significant treatment decision is made without a test result. A knee isn't listed for surgery without imaging; a bowel symptom isn't diagnosed without a scope; a heart murmur isn't managed without an echo. That makes diagnostics the narrowest point in most pathways — and a six-week diagnostic wait doesn't sit alongside your RTT wait, it sits inside it.
The arithmetic compounds. A typical routine pathway might be: referral, wait for first appointment, wait for a scan, wait for results and review, then wait for a theatre slot. If the scan step alone takes six weeks or more, a pathway that might have finished within the 18-week standard drifts well beyond it. It's a large part of why 1 in 12 people on the RTT list have waited 38.6 weeks or more.
Where the pressure is worst: MRI and endoscopy
The pressure isn't evenly spread across the 15 tests. MRI and endoscopy are the persistent trouble spots — MRI because demand from musculoskeletal, neurological and cancer pathways keeps rising faster than scanner capacity, and endoscopy because it needs specialist staff, procedure rooms and recovery time rather than just a machine. Audiology and echocardiography have also run long queues in recent years. Ultrasound tends to move faster because capacity is more widely distributed across hospitals and community settings.
Community diagnostic centres have added capacity and are generally credited with helping, but demand has grown alongside — referrals for imaging in particular keep climbing as GPs are encouraged to test earlier rather than refer and wait. The result is a queue that improves in absolute activity terms while barely moving in percentage terms: more tests are done each month than ever, and roughly a quarter of the queue still breaches six weeks.
Don't wait for the scan
The private route: what tests cost
Diagnostics are one of the areas where going private makes the biggest time difference — a scan is typically available within one to two weeks, often days. It's also one of the more affordable private purchases, whether self-pay or through insurance that includes diagnostics and scans cover:
| Test | Typical private self-pay price |
|---|---|
| MRI scan | £300–£500 |
| CT scan | £350–£800 |
| Initial consultation | £150–£300 |
If you're weighing it up, our guides to private MRI scans and private endoscopy cover the process, and the waiting times hub has the latest NHS data.
Frequently asked questions
What proportion of people wait six weeks or more for an NHS diagnostic test?
Around 1 in 4, according to NHS England's DM01 diagnostic waiting times data (January 2026). The operational standard is that fewer than 1% of patients should wait six weeks or more for one of the 15 key tests, so the current position is a long way from target.
What are the 15 tests in the DM01 diagnostic data?
DM01 covers imaging (MRI, CT, non-obstetric ultrasound, barium enema, DEXA), physiological measurement (echocardiography, electrophysiology, peripheral neurophysiology, sleep studies, urodynamics, audiology) and endoscopy (gastroscopy, colonoscopy, flexi sigmoidoscopy, cystoscopy). Together they gate most NHS treatment decisions.
Why do diagnostic waits make NHS treatment waits longer?
Because the diagnostic queue sits inside the referral-to-treatment pathway, not alongside it. Surgeons and physicians generally won't make treatment decisions without imaging or scope results, so a six-week wait for an MRI or colonoscopy directly extends the overall RTT wait for that patient.
Which diagnostic tests have the worst NHS waits?
MRI and endoscopy are the persistent pressure points — MRI because demand keeps outgrowing scanner capacity, endoscopy because it needs specialist staff and procedure rooms. Audiology and echocardiography have also carried long queues. Ultrasound generally moves faster.
How much does it cost to pay privately for a diagnostic test instead of waiting?
Indicatively, a private MRI costs £300–£500, a CT £350–£800 and an initial consultation £150–£300, typically available within one to two weeks. You can usually take private results back into the NHS for treatment, which makes self-pay diagnostics a common way to shorten a stalled pathway.