Levothyroxine 25mcg Tablets

Quick Facts Table

What Is Levothyroxine?

Levothyroxine is a synthetic (man-made) version of thyroxine (T4), a hormone naturally produced by the thyroid gland. It is used as a replacement hormone therapy in people whose thyroid gland does not make enough of its own hormone. Levothyroxine 25 mcg tablets are available as a generic medicine, such as Thyronorm 25 mcg, and also under the brand name Eltroxin. Both generic and branded versions contain the same active ingredient, levothyroxine sodium, and are manufactured to UK regulatory standards. The 25 mcg strength is often used as a starting dose, particularly in older adults or people with certain heart conditions, or as part of a dose adjustment plan directed by a prescriber.

What Is Levothyroxine Used For?

Levothyroxine is commonly prescribed for:

• Treating hypothyroidism (underactive thyroid) caused by conditions such as autoimmune thyroiditis, thyroid surgery, or radioactive iodine treatment

• Managing hypothyroidism that develops after treatment for an overactive thyroid

• Supporting thyroid hormone levels in some cases of thyroid cancer follow-up, only if prescribed by a healthcare professional

• Helping to manage congenital hypothyroidism in children, only under specialist medical supervision

Levothyroxine does not cure thyroid disease; it replaces the hormone your thyroid is not producing in sufficient amounts.

How Does Levothyroxine Sodium Work?

Levothyroxine sodium works by replacing the thyroid hormone (thyroxine) that the thyroid gland would normally produce. Once absorbed, it is converted in the body to triiodothyronine (T3), the active form of thyroid hormone. T3 helps regulate metabolism, energy production, and the function of the heart, brain, and other organs. In people with an underactive thyroid, this replacement helps restore hormone levels toward a normal range, which may help improve symptoms such as tiredness, weight changes, and low mood over time. Response to treatment is monitored through regular blood tests, and doses are adjusted gradually as directed by a prescriber.

Available Strengths And Forms

This page covers Levothyroxine 25 mcg tablets. Levothyroxine is also available in the following related strengths:

• Levothyroxine 50 mcg

• Levothyroxine 75 mcg

• Levothyroxine 100 mcg

• Levothyroxine 112 mcg

• Levothyroxine 125 mcg

The right strength for you depends on factors such as the severity of your condition, your age, body weight, heart health, and how your thyroid levels respond to treatment. Only a prescriber can determine the correct strength for your individual needs, and this may change over time based on blood test results.

How To Take Levothyroxine

• Always follow the instructions on your prescription label and the guidance given by your prescriber or pharmacist

• Levothyroxine is usually taken once daily, typically in the morning on an empty stomach, as directed

• Take the tablet with water, as advised in your patient information leaflet

• Do not increase, decrease, or stop your dose without speaking to your doctor first, even if you feel well or unwell

• If you are unsure about how to take your medicine, contact your pharmacist or prescriber before your next dose

• If you miss a dose, refer to the patient information leaflet or ask your pharmacist for guidance

Dosage Information

Levothyroxine dosing is individualised and depends on several factors, including:

• The condition being treated and its severity

• Your age (older adults are often started on lower doses)

• How your body responds to treatment, assessed through blood tests

• Other medicines you are taking

• Heart, liver, or kidney function, where relevant

Your prescriber will determine your starting dose and may adjust it gradually based on thyroid function test results. Do not change your dose without medical advice. This page does not provide personalised dosage instructions — always follow what has been prescribed for you.

Side Effects of levothyroxine sodium 25 mcg

Common Side Effects:
Side effects are more likely if the dose is too high for your needs. These may include:

• Headache

• Difficulty sleeping

• Feeling restless or agitated

• Increased sweating

• Diarrhoea

• Weight changes

• Rapid or irregular heartbeat (palpitations)

Serious Side Effects – seek urgent medical advice if you experience:

• Chest pain or a fast, irregular heartbeat

• Signs of an allergic reaction, such as swelling of the face, lips, tongue or throat, severe rash, or difficulty breathing

• Severe headache, vomiting, or vision changes

• Signs of overtreatment such as significant tremor, high fever, or extreme agitation

This is not a full list of side effects. Read the patient leaflet and speak to a pharmacist or doctor if you are concerned.

Warnings And Precautions

• Allergy: Do not take levothyroxine if you have a known allergy to levothyroxine sodium or any of the tablet's ingredients

• Pregnancy/Breastfeeding: Levothyroxine is often continued or required during pregnancy and breastfeeding, but doses may need adjustment — always speak to your doctor

• Heart problems: Caution is needed in people with heart disease, angina, or arrhythmias, as levothyroxine can affect heart rate

• Adrenal or pituitary conditions: Certain hormone conditions must be assessed and treated before starting levothyroxine

• Mental health: Tell your doctor if you have a history of anxiety or psychiatric conditions, as thyroid hormone changes may affect mood

• Diabetes: Levothyroxine may affect blood sugar control and diabetic medicine requirements

• Driving/machinery: Levothyroxine is not generally known to affect alertness, but if you feel unwell, dizzy, or experience palpitations, avoid driving or operating machinery until you feel better

Drug Interactions

Levothyroxine can interact with a number of other medicines and substances, including:

• Prescription medicines: Blood thinners (e.g. warfarin), diabetes medicines (insulin, oral hypoglycaemics), certain antidepressants, epilepsy medicines (e.g. phenytoin, carbamazepine), and oestrogen-containing therapies

• OTC medicines: Antacids, calcium supplements, and iron supplements can reduce levothyroxine absorption if taken too close together

• Herbal supplements: Some supplements may interact with thyroid hormone levels or absorption; always check with a pharmacist

• Food: Certain foods, particularly those high in soy or fibre, may affect absorption if taken at the same time

Tell your doctor or pharmacist about all medicines you take, including prescription, over the counter, and herbal products.

Who Should Not Use Levothyroxine?

Levothyroxine may not be suitable for people who:

• Have a known allergy to levothyroxine sodium or tablet excipients

• Have untreated adrenal insufficiency or untreated pituitary insufficiency

• Have untreated thyrotoxicosis (overactive thyroid)

• Have had a recent heart attack, uncontrolled heart disease, or certain arrhythmias, without specialist assessment

This is not a complete list. Your prescriber will assess your full medical history before prescribing levothyroxine.

UK Prescription Requirement

Levothyroxine 25 mcg Tablets is a prescription-only medicine (POM) in the UK. It should only be used with a valid prescription from an authorised healthcare professional. This ensures your thyroid function, dosage, and any other health conditions are properly assessed and monitored throughout treatment.

Storage

• Store below 25°C, in a cool, dry place away from direct heat and moisture

• Keep tablets in their original packaging to protect them from light

• Keep out of the sight and reach of children

• Do not use levothyroxine after the expiry date shown on the packaging

• Dispose of any unused or expired medicine via a pharmacy, not household waste

Active Ingredients info

Levothyroxine Sodium – Summary of Product Characteristics (EMC)

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FAQs

What is Levothyroxine 25 mcg used for?

Levothyroxine 25 mcg is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. It is often used as a starting dose or for fine-tuning thyroid hormone levels. Your prescriber will determine if this strength is right for you based on blood tests and your individual health needs.

Is Levothyroxine prescription-only in the UK?

Yes. Levothyroxine is classified as a prescription-only medicine (POM) in the UK. It can only be supplied against a valid prescription issued by a doctor or another authorised prescriber, ensuring your treatment is properly assessed and monitored.

What is the active ingredient in Levothyroxine 25 mcg?

The active ingredient is levothyroxine sodium, a synthetic form of the thyroid hormone thyroxine (T4). It works by replacing the hormone that an underactive thyroid gland is not producing in sufficient amounts.

Does 25 mcg of levothyroxine do anything?

Yes, 25 mcg is a genuine therapeutic dose, often used as a starting or adjustment dose, particularly in older adults or those with certain heart conditions. Its effect depends on individual thyroid hormone levels, so response should be monitored through blood tests as directed by your prescriber.

How long does Levothyroxine take to work?

Levothyroxine can take several weeks to show a noticeable effect, as thyroid hormone levels adjust gradually. Full benefits and stable hormone levels may take 4–6 weeks or longer to assess, which is why regular blood tests are used to guide dose adjustments.

What are the common side effects of Levothyroxine?

Common side effects can include headache, difficulty sleeping, restlessness, sweating, and changes in appetite or weight. These are often linked to the dose being higher than needed. Speak to your pharmacist or doctor if side effects persist or concern you.

Can I take Levothyroxine with other medicines?

Levothyroxine can interact with certain medicines, including blood thinners, diabetes treatments, antacids, and iron or calcium supplements. Always tell your doctor or pharmacist about all medicines, supplements, and herbal products you are taking before starting treatment.

Can I stop taking levothyroxine 25 mcg?

Do not stop levothyroxine without medical advice, even at a low 25 mcg dose. Stopping suddenly can cause hypothyroidism symptoms to return, including fatigue, weight gain and low mood. Some people may eventually reduce or stop under supervision, but this requires blood tests and monitoring by a GP or endocrinologist. Never adjust your dose independently, always consult a healthcare professional first.

Does 25 mcg of levothyroxine do anything?

Yes, 25 mcg is a genuine therapeutic dose, often used for mild hypothyroidism, older adults, or fine-tuning after larger doses. Though it seems small, it can meaningfully affect thyroid hormone levels and symptoms. Effects are usually assessed via blood tests after 6-8 weeks. If you're unsure it's working, discuss retesting with your GP rather than stopping or changing the dose yourself.

Where can I buy Levothyroxine online in the UK safely?

Levothyroxine is a prescription-only medicine, so it can only be purchased online through a registered UK pharmacy service after a valid prescription has been provided and verified. Always check that the online pharmacy is registered with the relevant UK regulatory body.

Medical Disclaimer

This content is for educational purposes only and does not replace medical advice. Always speak with a doctor, pharmacist, or qualified healthcare professional before starting, stopping, or changing any medicine.

Reference

• Electronic Medicines Compendium (EMC) — Levothyroxine Sodium Summary of Product Characteristics

• NHS — Levothyroxine medicine overview:

• MHRA — Medicines classification and product information (via GOV.UK)