Thyroxine (levothyroxine)
Also known as: Levothyroxine · T4
Thyroxine, also called levothyroxine, is a thyroid hormone replacement used when the thyroid gland is underactive. Some of my rheumatology patients are also on thyroid medicine, so I want to explain it clearly and gently.
Calm, careful medication review by a consultant rheumatologist.
Levothyroxine is not usually prescribed in my rheumatology clinic. Your endocrinologist or GP will normally guide the dose and monitoring. I share this page for patient education only.
What this medicine is
Levothyroxine is a man-made version of the natural thyroid hormone thyroxine (T4). It is taken as a daily tablet to top up the level of thyroid hormone in the body when your own thyroid gland is not making enough.
Uses and context
It is used mainly for an underactive thyroid (hypothyroidism), and after some thyroid surgery or thyroid cancer treatment. Some autoimmune conditions I look after can occur alongside autoimmune thyroid disease, so a small number of my patients are already on levothyroxine.
How this relates to rheumatology care
In clinic I check whether the thyroid is affecting your symptoms of tiredness, joint aches, muscle pain, or hair changes. If your thyroid dose has recently changed I like to know, because thyroid balance can affect how you feel overall. I do not adjust your thyroid dose myself; that is your prescribing doctor's role.
What safety checks may matter
Take it once a day, usually on an empty stomach
Keep at least 4 hours between levothyroxine and calcium, iron or antacid tablets
Regular thyroid blood tests (TSH, sometimes free T4) as advised
Tell every doctor and pharmacist that you take levothyroxine
Do not switch brand or stop the medicine without medical advice
Store tablets at room temperature, away from heat and moisture
Side effects and red flags
If you have emergency symptoms such as severe allergic reaction, breathing difficulty, chest pain, stroke-like symptoms, severe abdominal pain, vomiting blood, black stools, sudden vision loss, severe infection symptoms, or severe weakness or confusion, please seek urgent medical care first rather than waiting for a WhatsApp reply.
Chest pain, palpitations, or a very fast heartbeat
Severe tremor, sweating, anxiety, or unintended weight loss
Severe tiredness, cold intolerance, or swelling of the face and legs
Signs of allergic reaction such as rash, swelling of the face, or breathing difficulty
Things worth knowing day to day
Pregnancy or planning pregnancy: please tell your doctor early, as the dose often needs to be reviewed.
Some medicines and supplements (iron, calcium, some antacids, some cholesterol medicines) can affect absorption.
Do not double up if you miss a dose. Take the next dose at your normal time.
If you feel very unwell after a dose change, contact your prescribing doctor.
Questions patients often ask me about this medicine
Speak with me
If you take levothyroxine and are also being seen for a rheumatology concern, please message my clinic. I would like to understand how you are doing overall, without changing your thyroid plan.
Other medications used in rheumatology care
This page is for general education only and does not replace medical advice. Please consult a qualified healthcare professional for diagnosis and treatment. Do not start, stop, or change any medicine without advice from your doctor.