Thyroid Medication

Levothyroxine is synthetic thyroxine — chemically identical to the hormone your thyroid should be producing. It is taken once daily, usually for life, and when correctly dosed it restores normal function completely.

Liothyronine (T3) is occasionally used for the minority who remain symptomatic on levothyroxine alone. It is specialist-initiated in the UK, and we would refer rather than start it.

For an overactive thyroid, treatment is different — carbimazole, radioiodine or surgery — and endocrinology-led. We assess, test and refer.

• People with a raised TSH and low free T4 — overt hypothyroidism
• People with subclinical hypothyroidism and symptoms, positive thyroid antibodies, or a TSH above 10
• Anyone already on levothyroxine who feels unwell and wants their dose properly reviewed
• Women planning pregnancy or newly pregnant on levothyroxine — requirements rise and this is frequently missed

1. Testing before anything else

A full thyroid profile — TSH, free T4, and thyroid antibodies, which tell you whether this is autoimmune Hashimoto's and therefore likely to progress. Antibodies are often omitted and change how you interpret a borderline result.

2. Rule out the mimics

Ferritin, B12 and folate and vitamin D. Low iron and low B12 produce very similar symptoms and frequently coexist — treating the thyroid alone then leaves you still exhausted.

3. Starting and titrating

We start at an appropriate dose for your age and heart health, then recheck TSH at 6–8 weeks — not sooner, because the level takes that long to settle. Adjust and repeat until symptoms and bloods agree.

4. Ongoing monitoring

Annually once stable, sooner if anything changes.

Six to eight weeks between blood tests — not sooner

This is the number that matters, and testing earlier is the commonest reason titration goes wrong. TSH takes six to eight weeks to settle after any dose change, so a test at three weeks produces a figure nobody can act on — and frequently prompts a change that was not needed.

• Recheck 6–8 weeks after starting or changing the dose
• Repeat until symptoms and bloods agree, which often takes several rounds
• Annually once stable, and sooner if anything changes

How to take it, because absorption is where control is lost

• Empty stomach, 30–60 minutes before breakfast — or at bedtime, at least two hours after eating, which suits some people better and works equally well
• The same way every day. Inconsistent timing is a common cause of erratic results
• Iron, calcium, indigestion remedies and multivitamins block absorption — separate by at least four hours
• Coffee taken immediately with it reduces absorption. Wait half an hour
• Soya, and high-fibre supplements, also interfere

Aim for symptoms and numbers together

"Within the reference range" is not the same as "right for you". Most people do best with a TSH in the lower half of the range, and titration is frequently abandoned the moment a result lands anywhere inside it.

Equally, we do not simply push the dose up to chase symptoms. Over-replacement causes real harm — atrial fibrillation and reduced bone density over years — and if the numbers are good and you still feel unwell, the answer is usually something else rather than more levothyroxine.

Symptoms mean the dose is wrong

• Too much — palpitations, tremor, anxiety, heat intolerance, weight loss, disturbed sleep
• Too little — the original symptoms persisting

Pregnancy — the one not to miss

Levothyroxine requirements rise by around 25–50% in early pregnancy, and the dose needs increasing promptly. Tell us as soon as you have a positive test, or before trying.

Never stop levothyroxine in pregnancy — untreated hypothyroidism carries real risks for the baby.

Things that change the requirement

Starting or stopping oestrogen — HRT or the combined pill — raises it. So do significant weight change, and starting iron or calcium. Ageing tends to lower it.

Rule out the mimics before concluding it is the thyroid

Low iron and low B12 produce very similar symptoms and frequently coexist — treating the thyroid alone then leaves you still exhausted and convinced the treatment has failed.

• Ferritin — symptoms occur well above the anaemia threshold
• B12 and folate, and vitamin D
• Sleep apnoea, depression and perimenopause, all of which look like this
• Coeliac disease, which is commoner in autoimmune thyroid disease and impairs levothyroxine absorption

Antibodies change the interpretation

Thyroid antibodies tell you whether this is autoimmune Hashimoto's and therefore likely to progress. They are frequently omitted — and with a borderline TSH, a positive antibody result changes the decision.

Where liothyronine (T3) fits

A minority of people remain symptomatic on levothyroxine alone, and that is a real phenomenon rather than a complaint to dismiss.

T3 is specialist-initiated in the UK, and we would refer to endocrinology rather than start it. Before that step, it is worth being certain the dose is optimised, the timing is right, and iron, B12 and vitamin D are adequate — which resolves a good number of cases.

What we would advise against

• Desiccated thyroid extract — unlicensed in the UK, variable hormone content between batches, and not recommended by the British Thyroid Association. It is widely sold online and we do not prescribe it
• Iodine and "thyroid support" supplements — excess iodine can worsen thyroid disease, and these are not benign
• High-dose biotin, which interferes with thyroid blood tests and produces misleading results. Stop it several days before any test and say that you take it

An overactive thyroid is a different matter

Hyperthyroidism is treated with carbimazole, radioiodine or surgery, and is endocrinology-led. We assess, test and refer.

Subclinical hypothyroidism

A raised TSH with a normal T4 does not always need treating. Treatment is generally warranted with a TSH above 10, with positive antibodies, with symptoms, or in pregnancy — otherwise monitoring is often the better answer, and we will say so.

What you pay us

• £40 for the consultation
• A full thyroid profile including antibodies, plus iron, B12, folate and vitamin D, quoted before arranging. The antibodies and the mimics are the point of the testing
• £40 for each titration review, with bloods at 6–8 week intervals

Getting to the right dose usually takes two or three rounds, and it is worth knowing that before starting rather than being surprised by it.

What you pay the pharmacy

Levothyroxine is inexpensive. We earn nothing from what is prescribed.

One practical note: stick to the same manufacturer where you can. Some people notice a difference between brands, and it is a legitimate thing to ask a pharmacist about.

The NHS point, which matters here

In England, an underactive thyroid requiring levothyroxine qualifies you for a medical exemption certificate — which makes all your NHS prescriptions free, for everything, not just the thyroid.

Many people entitled to one have never applied. Prescriptions are free anyway in Scotland, Wales and Northern Ireland.

This is lifelong treatment with annual monitoring, and the NHS route is cheaper over years. Where we are useful is speed, and twenty minutes to titrate properly for someone whose dose has never been optimised.

Where not to spend money

• "Thyroid support" supplements and iodine — unnecessary at best, and excess iodine can worsen thyroid disease
• Desiccated thyroid extract bought online — unlicensed, variable content, and unmonitored
• Repeated private thyroid panels every few weeks. Testing more often than every 6–8 weeks produces numbers nobody can act on, and any service selling frequent panels is selling tests

Why do I have to wait six to eight weeks between blood tests?

Because TSH takes that long to settle after a dose change. A test at three weeks gives a number nobody can act on — and it frequently prompts a dose change that was not needed.

This is the commonest reason titration goes wrong, and waiting is genuinely the faster route to the right dose.

My results are "normal" but I still feel awful.

A common and legitimate complaint, and there are three usual explanations.

• The dose is inside the range but not optimal for you. Most people do best with a TSH in the lower half, and titration is often abandoned once a result lands anywhere inside the range
• Absorption. Timing, coffee, iron and calcium all matter more than people are told
• Something else. Low iron and low B12 produce almost identical symptoms and frequently coexist, as do sleep apnoea, depression and perimenopause

What is not the answer is simply pushing the dose up, which causes real harm over years.

How exactly should I take it?

Empty stomach, 30–60 minutes before breakfast — or at bedtime, at least two hours after eating. Either works; consistency is what matters.

Separate iron, calcium, indigestion remedies and multivitamins by at least four hours. Wait half an hour before coffee.

Will I be on it for life?

Usually yes, particularly with autoimmune Hashimoto's, which tends to progress.

It is replacement rather than medication in the ordinary sense — you are taking something your body should be making, and at the right dose it restores normal function completely.

Are there side effects?

At the right dose, no — and symptoms almost always mean the dose is wrong.

Too much causes palpitations, tremor, anxiety, heat intolerance and weight loss, and over years atrial fibrillation and reduced bone density. Too little means the original symptoms persist.

What are thyroid antibodies and why do they matter?

They tell you whether this is autoimmune Hashimoto's, which is likely to progress — and that changes how a borderline result is interpreted.

They are frequently omitted from testing, which is why we include them.

My TSH is slightly raised but T4 is normal. Do I need treatment?

Not always — and we will say so rather than treating a number.

Treatment is generally warranted with a TSH above 10, with positive antibodies, with symptoms, or in pregnancy. Otherwise monitoring is often the better answer.

I am pregnant, or trying. What should I do?

Tell us immediately, and never stop your levothyroxine.

Requirements rise by around 25–50% in early pregnancy and the dose needs increasing promptly — this is frequently missed. Untreated hypothyroidism in pregnancy carries real risks for the baby.

Can I have T3 (liothyronine)?

Possibly, and it is a real option for the minority who remain symptomatic on levothyroxine alone. It is specialist-initiated in the UK, so we refer rather than start it.

Before that, it is worth being sure the dose is optimised, the timing is right, and iron, B12 and vitamin D are adequate — which resolves a good number of cases.

What about natural desiccated thyroid?

We do not prescribe it. It is unlicensed in the UK, the hormone content varies between batches, and it is not recommended by the British Thyroid Association.

It is widely sold online, which is precisely the problem — unlicensed, unmonitored, and inconsistent.

Should I take iodine or a thyroid supplement?

No. Iodine deficiency is uncommon in the UK, and excess iodine can worsen thyroid disease rather than help it.

And stop high-dose biotin several days before any blood test — it interferes with thyroid assays and produces misleading results.

Does it matter which brand I get?

Some people do notice a difference between manufacturers. If you have been stable and something changes after a new pack, that is worth mentioning — asking your pharmacy to keep you on one supplier is a reasonable request.