Heidi Evidence vs OpenEvidence: Which One Can UK Doctors Actually Use?

If you are weighing Heidi Evidence against OpenEvidence from the UK, the choice is mostly settled for you — but not in the way a quick look at either website suggests.

OpenEvidence is not officially available here. Heidi Evidence is, for general questions asked outside a patient session — unless your account uses an NHS UK email, in which case Heidi excludes it entirely.

That last point matters more than anything else in this comparison for most readers of this site, and neither vendor's marketing leads with it.

OpenEvidence: withdrawn, not degraded

OpenEvidence withdrew from the United Kingdom and the European Union on 27 April 2026. The company pointed to regulatory uncertainty in those territories, the EU AI Act among them.

Two details matter more than the headline.

The first is that the restriction is deliberate rather than a temporary outage. It is a company-imposed geoblock, not a regulator-announced ban, and it covers existing accounts as well as new registrations. No public timetable for a return was found as of 30 August 2026.

The second is scale. OpenEvidence has reported handling in the order of 18 million clinical consultations a month before the withdrawal, and daily use by more than 40% of US physicians. Those are the company's own figures rather than independently audited ones, but they place this as a product that left at the height of its adoption.

We wrote about what filled the gap in Looking for an OpenEvidence alternative in the UK?.

Heidi Evidence: available, with three limits

Heidi Evidence answers clinical questions with citations attached, and it sits alongside Heidi's ambient documentation rather than being a separate destination.

Its UK position is more layered than "available" or "not available", and Heidi's own help documentation sets it out clearly. Three separate limits apply here.

1. In-session Evidence is unavailable. Heidi states plainly: "In-session Evidence is not available in the UK or EU." In-session Evidence is the version that runs inside Ask Heidi during an active consultation and can read the session transcript and linked patient details.

This is not the same as "you cannot use Evidence during clinic." Heidi's documentation is explicit that Evidence used outside a session is "fully available in the UK and EU on all plans", opened from the sidebar independently of any consultation. You can use it with a patient in front of you. What you cannot do is ask it a question from inside the session, with the patient's context attached.

2. Patient and session linking is unavailable. An Evidence conversation cannot be attached to a patient record or a live session. So the out-of-session tool works, but it works blind — it has no awareness of the case you are actually asking about.

3. NHS UK accounts are excluded from Evidence altogether. Heidi states that NHS UK accounts are excluded from Heidi Evidence, and from free trials that include it, and that an account registered with an NHS UK email address stays on its current plan. For a large share of UK clinicians, that turns a partial restriction into a complete one on their work account.

We covered the in-session restriction in more depth in Heidi Evidence in the UK: what the in-session restriction actually blocks.

Side by side, for a UK clinician

The two reasons in the bottom row are often reported as the same thing. They are not. One company judged the whole territory too uncertain; the other drew a line around a specific feature to stay outside medical-device regulation.

A note on how this is being marketed

One thing is worth knowing if you are reading vendor comparisons.

Heidi publishes its own OpenEvidence comparison page, updated in August 2026. It leads on Heidi being available wherever you practise, with no barriers or delays, and describes in-session Evidence as available in selected countries.

Both statements are defensible on their own terms, and Heidi's help centre documents the detail accurately. But read together by a UK clinician on an NHS address — who is excluded from Evidence entirely — that framing understates the position considerably.

We mention this not to score a point. Heidi's restriction is a deliberate regulatory choice rather than a product failing, and the company documents it openly one page away. But if you are choosing between tools on the strength of a comparison page, read the help centre as well.

The pattern behind both

It is tempting to read this as two companies making different calls. It is closer to two companies responding to the same regulatory environment in different ways, for reasons they describe differently.

Neither restriction has been attributed publicly to evidence quality or clinical safety findings, and we found none. One company withdrew from the territory; the other kept the product available and removed the feature that would have pulled it into device regulation.

For UK clinicians the practical consequence is the same either way: the tools you can reach are shaped by regulatory weather, and they change without much notice. That is worth factoring into how much of your practice you build on any one of them. We traced the wider pattern in UK doctors' AI tools 2026: two withdrawn, one restricted.

The problem neither of them solves

Both tools answer questions. That is the job they do.

But a question has to occur to you first. Neither tool tells you that the guideline you have been working to was updated last month, or that a trial has just landed in your specialty that changes the risk conversation you have been having for years. You cannot query your way to something you do not know exists.

That is a different problem, and it needs a different shape of tool: something that arrives, rather than something you visit.

The Monday Clinical Brief covers the five highest-impact journals in your specialty, across 31 of them. Every new paper from the past week, summarised, in one email each Monday morning. It costs £20 a year for your specialty, and £5 a year for each additional one. It is not a replacement for evidence lookup and we would not pitch it as one — it is what makes the lookup better aimed. We set out the distinction in Heidi Evidence vs The Monday Clinical Brief.

The bottom line

If you are a UK clinician choosing between Heidi Evidence and OpenEvidence, and you are not on an NHS UK account, Heidi Evidence is the one you can use. Know that it will not answer from inside a consultation and cannot see your patient's context, so plan your lookups accordingly.

If you are on an NHS UK email, Heidi excludes you from Evidence and OpenEvidence is not available here — so on that account, neither is an option today.

Then treat question-answering and keeping up as two separate jobs, because they are.

Availability details in this article were checked against OpenEvidence's and Heidi's own published documentation on 30 August 2026. Usage figures for OpenEvidence are the company's own reported numbers. Clinical AI availability in the UK has changed several times in 2026 — verify current status before relying on any tool.