🦋 Medication Guide

Thyroid hormone replacement

Levothyroxine

Replacing the thyroid hormone your body is not making enough of.

Levothyroxine is a synthetic version of thyroxine (T4), the main hormone produced by the thyroid gland. It is prescribed for hypothyroidism — an underactive thyroid — and is one of the most commonly prescribed medications in the world. When taken correctly, it restores normal thyroid function effectively.

What It Is Used For

✓ Hypothyroidism (underactive thyroid)

✓ After thyroid removal surgery

✓ After radioiodine treatment

✓ Thyroid cancer treatment (suppression doses)

✓ Hashimoto's thyroiditis

How It Works

Levothyroxine is identical to the thyroxine your thyroid gland produces. It is converted in the body to the active form (T3) that regulates metabolism, energy, heart rate, body temperature, and many other functions. By replacing the missing thyroxine, it restores the normal hormonal environment your body needs to function correctly.

Dosing — Typical Guidance

Starting dose

Usually 25–50 micrograms once daily — lower doses for older patients and those with heart conditions

Adjustment

Increased every 4–8 weeks based on TSH blood test results until the optimal dose is reached

Maintenance

Taken once daily for life in most cases — dose adjusted periodically based on TSH monitoring

Timing (critical)

Take on an empty stomach, 30–60 minutes before breakfast or food — food significantly reduces absorption

🍽️ Food & Timing: Take on an empty stomach, 30–60 minutes before your first food or drink of the day (water is fine). This is one of the most important rules for levothyroxine — food, coffee, and many supplements significantly reduce absorption.

⏰ Missed a dose? Take the missed dose as soon as you remember, unless it is close to the next day's dose. If you miss a full day, take it the next morning as usual. Do not double dose. Missing one or two occasional doses is not dangerous but regular missed doses will lead to under-treatment.

⚠️ Important Safety Note: Many substances interfere with levothyroxine absorption. Take it 4 hours apart from calcium supplements, iron tablets, antacids, and soy products. Coffee should be avoided for at least 30 minutes after taking levothyroxine.

Side Effects

Common (if dose too high)

Palpitations, tremor, weight loss, sweating, anxiety, diarrhoea, heat intolerance — these are signs of over-treatment (hyperthyroidism).

Contact your doctor — dose adjustment needed.

Common (if dose too low)

Fatigue, weight gain, cold intolerance, constipation, low mood — signs of under-treatment (continued hypothyroidism).

Inform your doctor — TSH rechecking and dose adjustment needed.

Rare

Allergic reactions to inactive tablet ingredients (fillers vary between brands)

Switch to a different brand — the active ingredient is the same.

Who Should Avoid This Medication

Who Should Not Take This (or Use With Caution)

⚠️ People with untreated adrenal insufficiency — thyroid replacement can trigger adrenal crisis (treat adrenal condition first)
⚠️ Uncorrected hyperthyroidism (overactive thyroid) — levothyroxine is the wrong treatment
⚠️ Use with extreme caution in significant heart disease — start at very low doses

Drug Interactions to Know

Medication / Substance	Why It Matters
Iron supplements	Significantly reduces levothyroxine absorption. Take iron 4 hours after levothyroxine.
Calcium supplements / antacids	Reduces absorption. Take 4 hours apart.
Coffee	Even a small amount of coffee taken within 30 minutes of levothyroxine reduces absorption significantly.
Cholestyramine / Colestipol (cholesterol medications)	Markedly reduces levothyroxine absorption. Take 4–6 hours apart.
Warfarin	Levothyroxine can increase the effect of warfarin. Closer INR monitoring when starting or adjusting levothyroxine.

Monitoring While on This Medication

TSH (Thyroid Stimulating Hormone)

Every 4–8 weeks after starting or dose change. Every 6–12 months once stable.

Free T4

Checked alongside TSH — particularly important in pregnancy and in people whose TSH target differs from the standard range.

Thyroid function in pregnancy

Monthly TSH testing in pregnancy — requirements increase significantly and dose adjustment is usually needed.

Frequently Asked Questions

Will I need to take levothyroxine for life?

Most people with hypothyroidism take levothyroxine for life. The underlying condition (usually autoimmune) does not resolve. However, the dose may change over time.

Can I take levothyroxine with my other medications?

Generally yes, but timing is important — especially with iron, calcium, and antacids. Always tell your doctor and pharmacist about all medications and supplements you take.

I feel fine — do I still need to take it?

Yes. Hypothyroidism returns when levothyroxine is stopped, even if you feel well. The medication is managing the condition — it does not cure it. Do not stop without medical advice.

Does levothyroxine cause weight loss?

It can help restore weight to normal if weight gain was due to uncontrolled hypothyroidism. It is not a weight loss medication and should not be taken for this purpose by people with normal thyroid function.

Can I take it during pregnancy?

Yes — and it is essential. Uncontrolled hypothyroidism during pregnancy increases miscarriage risk and affects fetal brain development. Dose requirements increase in pregnancy — monthly TSH monitoring is needed.

Questions about your medication?

Our doctors and pharmacists can review your prescription, explain your treatment, and address any concerns — confidentially.

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