Many people in the UK now see their blood test results in the NHS App before they've spoken to anyone about them. A result appears, sometimes with a label like "abnormal" or a flag next to a number, and no explanation alongside it. That experience can be unsettling, so let's explain, in general terms, what such a flag does and doesn't mean.
What a Flag Actually Indicates
When a result is flagged, it generally means the value falls outside the reference range for that test. That's it. The flag is the system noting "this number is outside the usual range," not the system making a judgement about your health.
Why Results Get Flagged Automatically
The flagging is automatic. A computer compares your number to the reference range and marks anything outside it. The system has no knowledge of your medical history, your medications, why the test was ordered, or the dozens of ordinary things that can nudge a result. It's a simple comparison, applied the same way to everyone.
That's a useful safety feature, because it draws attention to results worth a look. But it also means flags appear for results that turn out to be entirely expected once a clinician sees the full picture.
Why You Might See a Result Before Your GP Has
Results can land in the app as soon as the laboratory releases them, which can be before your GP practice has reviewed them. So a flag in the app doesn't mean your GP has looked and is worried; often it simply means the result has arrived. If action is needed, your practice has its own processes for following up on results that require it.
What to Do With a Flagged Result
- Try not to jump to conclusions from the flag alone. It's a prompt for context, not a diagnosis.
- Look at the units and the range on the result itself, which are shown together and belong together.
- If you're unsure or concerned, ask your GP practice. Interpreting what a result means for you specifically is exactly what they're there for.
- For non-emergency advice, NHS 111 is available; in an emergency, call 999.
The Bottom Line
An "abnormal" flag on the NHS App means a number fell outside the usual range, applied automatically and without context. It is a reason to ask a question, not a reason to assume the worst. The meaning of any individual result comes from a clinician looking at the whole picture, not from the flag itself.