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17 Jul 2026

Do you need to declare an undiagnosed condition for travel insurance?

We explain why millions of travellers could unintentionally void their cover and end up out of pocket

Ravi GhelaniConsumer writer & producer

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Nearly 1.9 million patients in England were waiting for tests or scans to help diagnose a health problem at the end of May 2026, according to NHS England figures.

Long waits for assessments and more people stuck in ‘diagnostic limbo’ mean some travellers are unsure about what they must disclose when buying a policy.

Co-op Insurance has previously found that around 16 million UK adults did not realise this could invalidate their travel insurance.

Here, Which? explains when an undiagnosed condition needs to be declared, how this affects your cover, and what to do if you’re struggling to find an insurer who'll cover you.

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What is an undiagnosed medical condition?

Insurers class an undiagnosed condition as any health issue that's being investigated but doesn't yet have a confirmed diagnosis. This can include:

symptoms you’ve spoken to a GP about
referrals for tests or scans
ongoing investigations for physical or mental health concerns
waiting lists for assessments, such as ADHD or autism
suspected conditions your doctor is monitoring.

Find out more: best travel insurance companies and policies

Can it invalidate your cover?

Yes. If you buy travel insurance without declaring a health issue that's still being investigated, your policy could be treated as invalid.

Insurers expect you to disclose any symptoms, referrals or tests that are underway, even if you don't yet have a diagnosis.

If you make a claim and the insurer later discovers you were waiting for medical investigations, it may refuse to pay out. This can apply even if the claim is unrelated, leaving you to cover costs yourself.

If you're unsure whether to declare something, check with your insurer before you travel. It's always better to ask than risk a rejected claim.

Find out more: best travel insurance for over-65s

Why do travellers get caught out?

People often assume they only need to tell their insurer about confirmed illnesses, not symptoms, referrals or tests that are still in progress.

But this can be a risky assumption. Co-op Insurance previously found that around one in five travellers had an undiagnosed condition, including people waiting for assessments or tests for health concerns.

This can leave travellers in a grey area: they may not have a diagnosis yet, but the insurer may still expect them to declare what is being investigated.

There is also confusion about whether an undiagnosed condition matters if it feels unrelated to the trip. If in doubt, check with your insurer before you travel, as failing to declare something relevant could put your cover at risk.

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Getting cover if you have health concerns

If you have a diagnosed condition or you're still waiting for tests or assessments, you may need to look beyond standard travel insurance policies.

Many insurers will ask extra screening questions or may not offer cover at all if your health status is uncertain.

Here are the steps worth taking:

Use a specialist medical travel insurer Some insurers focus on covering travellers with complex or ongoing health issues. They carry out detailed medical screenings, which can help you find a policy that better matches your situation.
Call before you buy If you're unsure how to declare your symptoms or referral, speak to the insurer directly. They can tell you what information they need and whether they can offer cover.
Check policy exclusions If you have an undiagnosed condition, some policies may offer cover but exclude claims linked to that specific issue. Make sure you understand what is and is not included before you travel.
Compare policies carefully Premiums can vary widely depending on your medical history, so it's worth comparing options from multiple providers.

For more help finding the right provider, see the best travel insurance for people with medical conditions.