Health insurance is not a substitute for travel insurance and should not be relied upon to cover all medical expenses incurred while on holiday, health insurers warn.

Travellers often decide to forgo the cost of travel insurance on the basis that their medical expenses will be covered by their health insurer, with some believing that the additional cover provided by travel insurance, such as compensation for lost or stolen baggage, travel delays and missed connections, are non-essential extras.

This view is encouraged by the fact that some policies may offer as little as €25 for every 12-hour period customers are delayed, up to a maximum of less than €100. That's not much to look forward to getting your hands on once the damage has been done and a holiday has been ruined by a delay on departure.

Holiday-makers may also decide their luggage, more likely to contain T-shirts, bikinis and beach towels than expensive items, simply isn't worth insuring.

However, travellers who take short cuts on insurance may leave themselves out of pocket in the event of illness or an accident.

VHI Healthcare automatically covers overseas emergency hospital expenses of up to €65,000 under its plans A to E and up to €100,000 under its core plans under what it calls VHI Assist.

If transport back to Ireland is required for medical treatment, it will cover the cost up to a limit of €1.27 million.

But VHI still advises customers to buy an additional travel insurance policy before going on holiday as their medical expenses may exceed these amounts.

"The cover is a contribution towards your care, but in terms of being covered fully you need additional travel insurance," says Ms Tara Buckley, general manager of corporate communications for VHI. Hospital care can cost €11,000 a day in the US, she notes.

"Certainly, in some parts of the world, it wouldn't be long before you use up the cover."

Bupa's Essential and Essential Plus policies covers up to €55,000 for emergency overseas medical expenses, while its Health Manager product covers up to €65,000.

A spokeswoman for Bupa, Ms Kate O'Keeffe, confirmed the cover was not a substitute for travel insurance.

"It would represent a very small proportion of our claims," she says.

By contrast, cover for medical expenses under travel insurance policies, including emergency travel expenses if policyholders need to be airlifted back home, ranges from about €2 million to €13 million.