Key takeaways

  • Blood tests measure TSH and T4 when an underactive thyroid is suspected. A GP may also examine the neck and ask about recent pregnancy or thyroid and autoimmune conditions in the family. NHS
  • Levothyroxine replaces missing thyroid hormone, usually for life. Regular blood tests check the prescription even when symptoms are controlled. NHS
  • Report nausea, diarrhoea, headaches or sleep problems. These are among the effects of the wrong levothyroxine amount. NHS
  • Breakfast and coffee affect how levothyroxine is taken. NHS advice is an empty stomach, 30 to 60 minutes before the first meal or a caffeinated drink. Follow the pack instructions. NHS levothyroxine
  • Mention supplements before blood tests. Biotin, vitamin B7, can affect thyroid test results. Calcium, iron and other medicines also belong in the treatment discussion. NHS levothyroxine
  • Report excessive sweating and poor heat tolerance during treatment. SPS advises hydration and possible thyroid-control review if symptoms suggest over-replacement with dehydration. SPS

Feeling cold in a heavily air-conditioned office is easy to explain away. So are tiredness and weight gain. Mild symptoms are easy to miss, which is why an underactive thyroid can be diagnosed late. Blood tests settle the question; the right replacement treatment should allow a normal life.

What does an underactive thyroid feel like?

Mostly like being run down, which is why it is so often attributed to something else.

The NHS describes hypothyroidism as a common condition where the thyroid gland in your neck does not make enough hormones, causing symptoms like tiredness and weight gain, and states directly that symptoms may be mild and may not be easy to notice. Common symptoms include feeling extremely tired and feeling cold more than usual.

Feeling cold more than usual is a symptom that hides especially well here, where buildings are heavily air-conditioned and being cold indoors is entirely normal. Someone who is always reaching for a cardigan in an office is unlikely to think of their thyroid, and nobody around them will suggest it either.

Symptoms worth taking together rather than individually:

  • persistent tiredness that rest does not fix
  • feeling cold when others are comfortable
  • weight gain without a change in eating
  • dry skin and brittle hair or nails
  • constipation
  • low mood or difficulty concentrating
  • heavier or irregular periods

Any one of these on its own is unremarkable. Several together, especially persisting, is a reason to ask for a blood test rather than to keep explaining them away.

How is it diagnosed?

With a blood test, after an examination that may include your neck.

The NHS describes a neck examination for swelling and blood measurements of thyroid-stimulating hormone (TSH) and thyroxine (T4). The GP also asks about recent pregnancy and thyroid or autoimmune conditions in the family. Some people need specialist tests. NHS

The two measurements answer different questions. TSH is the signal the brain sends to the thyroid, and it rises when the thyroid is underperforming. T4 is the hormone the thyroid itself produces. Reading them together is what distinguishes an underactive thyroid from other causes of the same symptoms.

This is why self-diagnosis does not work here and why symptom checklists online are unhelpful in both directions. The symptoms are shared with anaemia, vitamin D deficiency, depression, sleep problems and simply being overworked. The blood test is what separates them.

What does treatment involve?

Levothyroxine tablets, usually for life, with regular blood tests to confirm the dose.

An underactive thyroid is usually treated with medicine that replaces the hormone your body cannot produce, and that medicine is usually levothyroxine tablets. The NHS is clear about duration: you will usually need to take them for the rest of your life to prevent symptoms returning, and you should be able to live a normal life.

The part that gets underestimated is dose monitoring. You will have regular blood tests to check you are on the right dose, because being on the wrong dose can cause side effects such as feeling or being sick, diarrhoea, headaches or problems sleeping. If you have side effects, that is a conversation with your GP or pharmacist rather than a reason to stop.

If you have moved countries while taking levothyroxine:

  • Continuity of monitoring matters. If your last thyroid blood test was in another country a while ago, arranging one locally is worth doing.
  • Consistency of product matters. Levothyroxine has a narrow margin between doses that work and doses that do not, so tell your prescriber if the brand or presentation you are given changes.

The NHS levothyroxine guide describes tablets and oral solution. Tablets are swallowed whole with water; the liquid is measured with the supplied spoon or syringe. Its timing advice is an empty stomach, 30 to 60 minutes before breakfast or a caffeinated drink, at a consistent time. Check the leaflet for your product. NHS

Tell the prescriber about calcium, iron, antacids, omeprazole, sertraline and other medicines or supplements. Biotin, also called vitamin B7, can affect the thyroid tests themselves. Tell the doctor about pregnancy too; additional blood tests may be needed. NHS

What about an overactive thyroid?

An overactive thyroid makes too much hormone and needs treatment that reduces hormone production.

Hyperthyroidism means the gland produces too much hormone. Symptoms tend to be weight loss despite normal eating, feeling hot and sweating, a fast or irregular heartbeat, anxiety or irritability, tremor and difficulty sleeping.

It is treated with medicines that reduce hormone production, commonly carbimazole, and sometimes with other approaches depending on the cause. The catalogue also lists thiamazole, which is the same class.

Feeling hot and sweating heavily is another symptom that camouflages itself here, since so does everyone else in August. As with the underactive form, the distinguishing feature is the pattern taken together and the blood test that confirms it.

Does the climate interact with thyroid treatment?

Levothyroxine may contribute to sweating and heat intolerance; dehydration can prompt a review of thyroid control.

NHS Specialist Pharmacy Service guidance notes that levothyroxine may contribute to excessive sweating and heat intolerance, and advises maintaining hydration, with consideration of reviewing thyroid control if symptoms suggest over-replacement due to dehydration.

In practice: if you are on levothyroxine and find summer notably harder to tolerate than the people around you, that is worth mentioning at your next review rather than accepting. It may be the climate. It may also be that your dose needs checking.

Storage applies as it does to everything else, and is covered in storing medicine in a Gulf summer.

Do and don’t

Do:

  • Ask about TSH and T4 tests when several symptoms persist. Mention recent pregnancy and thyroid or autoimmune conditions in the family. NHS
  • Arrange local blood-test monitoring if your last review was abroad. Tell the prescriber if your levothyroxine brand or presentation changes.
  • Bring the supplement list: biotin can affect thyroid tests, and calcium and iron may interact with treatment. NHS
  • Report nausea, diarrhoea, headaches, sleep problems or unusually difficult heat tolerance. Keep regular blood-test appointments even when you feel well.

Don’t:

  • Dismiss persistent tiredness, or substitute an online symptom checklist for testing. Anaemia, vitamin D deficiency, sleep problems and depression have overlapping symptoms.
  • Stop levothyroxine because symptoms are controlled, or change the amount yourself. Both under-replacement and over-replacement cause problems.
  • Measure an oral solution with an improvised spoon; use the supplied spoon or syringe. NHS
  • Leave breakfast or caffeine out of the timing discussion. The NHS advice is 30 to 60 minutes beforehand on an empty stomach; check your own leaflet. NHS

Match a continuing prescription by its ingredient and strength.

The thyroid health category lists what is stocked here, and hypothyroidism and hyperthyroidism approach it from the diagnosis. The ingredients index maps active ingredients to brands, which matters for levothyroxine where consistency of product is worth attention.

MedicForce option: our thyroid listings show active ingredient and strength, which is the detail to match when continuing a prescription started elsewhere.