An underactive thyroid does not stop you applying for life insurance; insurers ask about it, and about an overactive thyroid, and the questions they publish are mostly practical: when it was diagnosed, whether a cause is known, what treatment you take and whether it has settled. Not sure how your thyroid history reads on paper? The form on this page is five short fields, and afterwards, at no cost, a rep from an FCA-authorised broker rings to go over it.

What does an insurer mean by an underactive thyroid?

The NHS (page last reviewed 28 April 2025) calls it "a common condition where the thyroid gland in your neck does not make enough hormones". It says the main cause in the UK is an autoimmune condition called Hashimoto's disease, and that the usual treatment is levothyroxine tablets, with regular blood tests to check the dose is right.

Insurers' guides for advisers describe it in much the same terms. Royal London's guide for advisers says "Hypothyroid is a condition in which the body lacks the hormone thyroxine." Guardian's underwriting guide for advisers describes two types, underactive (hypothyroidism) and overactive (hyperthyroidism), and says the treatment for hypothyroidism is hormone replacement tablets called levothyroxine. Both are adviser material, written for professionals rather than the public, but they show what the insurers want to hear from you.

Where does the thyroid question turn up on an application?

It depends on the insurer, and it is not always a question about the thyroid by name.

  • Royal London's Personal Menu Plan application form for advisers (P1A0023/24), in its section on physical health in the last five years, puts it under "Any disorder of the kidney, bladder, prostate or thyroid", with "Over or under-active thyroid" listed as one of the things included. It asks you to name the condition and fill in an extra medical details section.
  • Legal & General's personal application form for advisers (OLP Connect SA26, W11904 02/26) asks only people applying for critical illness cover or income protection whether a health professional has seen them in the past five years for "any condition affecting your thyroid".
  • Guardian's guide for advisers says "There isn't a specific question for thyroid disorder", but that the cause may be the subject of a question, and that a wider question about treatment, specialists or blood tests in the last three years may lead to it being disclosed.

The look-back period differs by form, and so does the trigger: a named condition, contact with a health professional (on that Legal & General form, only for those two types of cover), or a medication and tests question. A broker can tell you which wording applies to the policy you are looking at.

Which details do insurers ask you to have to hand?

Royal London's list of what helps on an application form for hypothyroidism is: date of diagnosis; whether an underlying cause has been identified; the nature and severity of symptoms and the date of the last symptoms; details of any treatment including surgery; whether the condition has stabilised on treatment; and whether there has been any time off work.

Guardian's list of what it will ask about overlaps with that and adds several more: when your first symptoms began, whether you are awaiting tests or a hospital referral, the outcome of your last GP consultation and the date and outcome of any specialist referral, whether you have been diagnosed with heart rhythm problems or eye problems, when you started your medication, and whether there is a family history of thyroid cancer.

Your GP surgery or hospital letters are the usual place to find dates. If you cannot remember one exactly, say so on the call rather than guess.

Does it matter that treatment has stabilised?

Both guides put control on the list. Royal London asks "Whether the condition has stabilised on treatment", and Guardian asks "Whether their condition is well controlled", along with the nature of treatment and the date medication began. How the answer affects the terms is for each insurer to decide on your whole application. How a recent dose change would be viewed is a question the broker can put to insurers on your behalf when they ring.

What about an overactive thyroid or Graves' disease?

The NHS (page last reviewed 11 April 2023) describes Graves' disease as an autoimmune condition and says about 4 in every 5 people with an overactive thyroid have it. How a particular insurer reads a Graves' diagnosis is for a broker to explain on a free call.

Guardian groups overactive thyroid under the same heading and lists treatments that can include medication, radioiodine or surgery to remove all or part of the gland, with hormone replacement needed if the whole gland is removed. The same list of questions covers both types, and it includes the date of any surgery or radioiodine treatment.

Do you have to mention it?

Yes, where the question asks. Under the Consumer Insurance (Disclosure and Representations) Act 2012, you must take reasonable care that none of your answers misrepresents anything to the insurer. Legal & General's form says that if you do not answer "fully and accurately", it is "very likely" that "a claim may not be paid and your policy may be amended or cancelled". The law behind it is in what you must disclose when applying, and medical questions for life insurance shows how health questions are usually put.

When the first reply is a delay, a loading or a no

An extra charge, a delay or a refusal comes from one insurer reading one set of answers. What a loading means and what to do after a decline pick up from there, while life insurance with medical conditions gives the wider picture. Hashimoto's and Graves' are both autoimmune conditions, and life insurance with lupus or another autoimmune disease covers that wider group. Before applying, you could use the quick enquiry form here and have a broker with FCA authorisation phone to discuss your thyroid history, no cost.

Frequently asked questions

Do I have to tell an insurer I take levothyroxine?

Royal London's form asks about "Over or under-active thyroid", and Guardian's treatment question covers medication taken for more than a month. Taking tablets for a thyroid condition is the sort of thing those questions reach.

Is Hashimoto's disease the same as an underactive thyroid on a form?

The NHS names Hashimoto's disease as the main UK cause of an underactive thyroid. Royal London asks whether an underlying cause has been identified, so give the name your doctors use alongside "underactive thyroid".

Will an underactive thyroid raise my premium?

That depends on the insurer and on what you tell it about diagnosis, treatment and control. A broker can ask insurers about your history during the free call-back.

Sources

  • NHS, Underactive thyroid (hypothyroidism) (page last reviewed 28 April 2025), read 26 October 2026. nhs.uk
  • Royal London, Medical conditions tool (adviser material, undated), read 26 October 2026. adviser.royallondon.com
  • Royal London, Personal Menu Plan application form (P1A0023/24, adviser document), read 20 October 2026. adviser.royallondon.com
  • Legal & General, OLP Connect Application Form (SA26) (W11904 02/26, adviser document), read 20 October 2026. legalandgeneral.com
  • NHS, Overactive thyroid (hyperthyroidism) (page last reviewed 11 April 2023), read 26 October 2026. nhs.uk
  • legislation.gov.uk, Consumer Insurance (Disclosure and Representations) Act 2012, section 2, read 26 October 2026. legislation.gov.uk
  • Guardian, Underwriting guide (adviser material, undated), read 26 October 2026. adviser.guardian1821.co.uk