Levothyroxine
Levothyroxine is a synthetic form of thyroxine (T4), the hormone your thyroid gland normally makes. In the UK it is the standard treatment for an underactive thyroid (hypothyroidism) when your thyroid does not produce enough hormone.
This medicine is part of the Blood pressure, cholesterol & related category.
Generic name: levothyroxine
Quick answers
Short replies to searches people often run before speaking to a clinician. For the overview of what the medicine is used for, see the short summary under the page title above.
What is it for?
Levothyroxine is a synthetic form of thyroxine (T4), the hormone your thyroid gland normally makes.
How long does it take to work?
Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review.
What are common side effects?
When the dose is right, most people do not feel “side effects” from levothyroxine itself — previous underactive thyroid symptoms such as tiredness and weight gain should improve over weeks to months.
Can you take paracetamol or ibuprofen with it?
Ask your GP or pharmacist before taking Levothyroxine with paracetamol or ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
More about what Levothyroxine is used for
Levothyroxine is a synthetic form of thyroxine (T4), the hormone your thyroid gland normally makes. In the UK it is the standard treatment for an underactive thyroid (hypothyroidism) when your thyroid does not produce enough hormone.
It may also be used after thyroid surgery or radioactive iodine, or for other reasons as directed by an endocrinologist or GP.
How does Levothyroxine work, and how long does it take to work?
Taken daily, it replaces missing thyroid hormone so metabolism, energy, heart rate, and many body processes can return towards normal levels over time.
Dose is individual and usually adjusted using blood tests (TSH and often free T4) rather than symptoms alone in the early stages.
How and when should you take Levothyroxine?
Levothyroxine is usually taken once daily on an empty stomach, often 30–60 minutes before breakfast, with water — follow your leaflet, as advice on timing with food and drinks such as coffee can affect absorption.
Try to take it at the same time each day. Swallow tablets with water; some people use liquid or dispersible forms if prescribed.
What are the common side effects of Levothyroxine?
When the dose is right, most people do not feel “side effects” from levothyroxine itself — previous underactive thyroid symptoms such as tiredness and weight gain should improve over weeks to months.
If the dose is too high, you may notice symptoms similar to an overactive thyroid, such as palpitations, tremor, anxiety, sweating, or weight loss — report these to your GP.
Serious side effects of Levothyroxine — when to get urgent help
Chest pain, severe palpitations, or collapse need urgent medical assessment — especially if dose may be too high or if you have heart disease.
Allergic reactions to the tablet ingredients are uncommon but possible.
What if you miss a dose of Levothyroxine?
If you forget a dose, take it when you remember unless it is close to the next day’s dose — then skip the missed one. Do not double up unless your prescriber says so.
If you miss several doses, contact your GP for advice.
Who should not take Levothyroxine?
Levothyroxine is not used to treat an overactive thyroid in the usual way. Untreated adrenal insufficiency needs treatment before starting thyroid hormone in some situations — your prescriber checks this.
Tell your doctor about heart disease, osteoporosis, diabetes, and all medicines including calcium, iron, and indigestion remedies that can affect absorption.
Can you take paracetamol or ibuprofen with Levothyroxine? — other interactions
Calcium, iron, some antacids, colestyramine, and some epilepsy medicines can reduce levothyroxine absorption if taken together — your pharmacist may advise spacing doses by several hours.
Warfarin effect can change when thyroid levels shift — your clinic may monitor INR more closely after dose changes.
Levothyroxine in pregnancy and breastfeeding
Dose often needs adjustment in pregnancy; tell your midwife or GP early if you are pregnant or planning pregnancy. Levothyroxine is commonly continued in pregnancy when needed.
It is generally compatible with breastfeeding at prescribed doses.
Blood tests and monitoring on Levothyroxine
Blood tests are used to guide dose, especially after starting, changing strength, or in pregnancy. Attend thyroid reviews when your practice requests them.
What might your GP prescribe instead of Levothyroxine?
Most people in the UK use levothyroxine tablets. Liothyronine (T3) or combination therapy is reserved for selected cases under specialist care.
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Frequently asked questions about Levothyroxine
People also ask — common Google searches
- What is Levothyroxine used for?
- Levothyroxine is a synthetic form of thyroxine (T4), the hormone your thyroid gland normally makes. In the UK it is the standard treatment for an underactive thyroid (hypothyroidism) when your thyroid does not produce enough hormone.
- How long does Levothyroxine take to work?
- Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review. Always follow your prescriber’s follow-up plan.
- Can you take Levothyroxine with paracetamol or ibuprofen?
- Ask your GP or pharmacist before taking Levothyroxine with Paracetamol or Ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
- What are the side effects of Levothyroxine?
- When the dose is right, most people do not feel “side effects” from levothyroxine itself — previous underactive thyroid symptoms such as tiredness and weight gain should improve over weeks to months. See the sections below for more detail, including serious side effects and when to seek urgent help.
- Can I drink coffee with levothyroxine?
- Coffee and some foods can reduce how much levothyroxine you absorb if taken at the same time. Many people take the tablet with water and wait before breakfast — follow your leaflet or pharmacist’s advice.
- How long until I feel better on levothyroxine?
- Symptoms often improve gradually over several weeks after the correct dose is reached. Blood tests help your GP fine-tune the dose — tell them if symptoms persist.
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