Levothyroxine – Medicine Information for Patients in Australia
Basic Product Information
| International Non-proprietary Name (INN) | Levothyroxine sodium |
| Australian Brand Names | Eutroxsig®, Oroxine®, Eltroxin® |
| ATC Code | H03AA01 |
| Available Forms & Strengths | Tablets: 25 mcg, 50 mcg, 75 mcg, 100 mcg, 200 mcg |
| Manufacturers | Alphapharm, Aspen Pharma, Sigma Pharmaceuticals, others |
| Prescription/Legal Status | Prescription Only Medicine (Schedule 4 – S4, PBS reimbursed) |
Mechanism of Action
For Patients:
Levothyroxine is a synthetic form of thyroxine (T4), a hormone normally made by your thyroid gland. It replaces or supplements this hormone in your body if your thyroid is underactive (hypothyroidism), helping to regulate energy, metabolism, and many “day-to-day” body functions.
For Healthcare Professionals:
Levothyroxine is metabolically deiodinated to triiodothyronine (T3), which binds to nuclear thyroid hormone receptors, triggering transcription cascades that regulate diverse physiological processes. It suppresses pituitary TSH release via feedback inhibition, restoring euthyroid status in deficiency states.
Pharmacokinetics
- Absorption: Oral bioavailability is 40-80%; best absorbed on an empty stomach. Absorption is reduced by certain foods, medicines, and malabsorption syndromes.
- Metabolism: Mainly metabolised by the liver and kidneys, with peripheral deiodination to active T3.
- Elimination Half-life: 6–7 days (approximately 3–4 days in hyperthyroidism; up to 9–10 days in hypothyroidism).
- Duration of Action: Steady-state typically reached after 6–8 weeks of consistent dosing.
- Excretion: Faecal and renal.
Use in Everyday Life and Best Practices
Levothyroxine is typically taken once daily, ideally first thing in the morning. For most Australian adults, the usual starting dose is 50–100 mcg per day, with adjustments every 4–6 weeks based on blood tests and clinical response.
- Take your tablet whole, with a glass of water.
- Try to take it at the same time each day for best results.
- Do not suddenly stop or change your dose without consulting your doctor.
- Your pharmacist or doctor will provide regular reviews and blood checks to ensure your dose remains optimal, especially if your circumstances or other medicines change.
In Australia, regular supply is available through community pharmacies, and most brands are listed on the PBS (Pharmaceutical Benefits Scheme) for eligible patients.
Dosing: Morning vs Evening
- Most specialists recommend taking Levothyroxine first thing in the morning, at least 30–60 minutes before any food or beverage (except water), to maximise absorption.
- Some patients may prefer evening dosing (at least 3 hours after the last meal). Research shows this can be as effective if taken consistently, but morning dosing remains preferred for convenience and habit-building.
- Consistency is crucial: always take your dose at the same time and relation to meals each day.
Tips: Set a phone reminder. Leave your tablets on the bedside table as a visual prompt.
Taking With Food or on an Empty Stomach
For optimal absorption, take Levothyroxine on an empty stomach, ideally 30–60 minutes before breakfast, tea, coffee, or any tablets. Foods common in English diet, especially those high in fibre (like bran, wholegrain breads, or oats), soy products, and coffee—can reduce how much medicine enters your body. If you forget and take it with food occasionally, don’t worry—just try to return to your usual routine as soon as possible.
Interaction Warnings
| Item | Effect | Recommended Action |
|---|---|---|
| Iron/calcium supplements, antacids | Reduce absorption of Levothyroxine | Take at least 4 hours apart from Levothyroxine |
| Coffee, soy, high-fibre foods | Reduce absorption | Take Levothyroxine before these foods |
| Warfarin | May increase effects of warfarin | Monitor INR closely, inform your GP |
| Anti-epileptics (e.g., carbamazepine, phenytoin) | Increase metabolism of Levothyroxine | May require a dose adjustment |
| Antidepressants (SSRIs, tricyclics) | Variable; possible interaction | Monitor for clinical effect |
| Alcohol | Generally safe in moderation | Excess alcohol can affect liver metabolism |
Indications for Use
| Indication | Official (TGA) | Off-label |
|---|---|---|
| Primary hypothyroidism (including Hashimoto’s disease) | ✓ | — |
| Congenital hypothyroidism | ✓ | — |
| Post-thyroidectomy or radioiodine therapy suppression | ✓ | — |
| Subclinical hypothyroidism | — | Considered in select cases |
| Thyroid cancer (as part of suppressive therapy) | ✓ | — |
| Goitre (benign, non-toxic) | ✓ | — |
| Mental health benefits, weight loss | — | Not recommended |
Dosing by Clinical Indication
| Indication/Population | Starting Dose | Titration/Maintenance | Notes |
|---|---|---|---|
| Adult hypothyroidism | 50–100 mcg once daily | Increase by 25–50 mcg every 4–6 weeks | Adjust by blood TSH, FT4; typical maintenance 100–200 mcg |
| Paediatric (congenital, acquired) | 10–15 mcg/kg/day for neonates | Age-dependent adjustments | Strict specialist supervision |
| Elderly or severe/chronic conditions | 12.5–25 mcg once daily | Increase gradually | Risk of cardiac events—start low, go slow |
| Thyroid cancer (suppression) | ~150–200 mcg once daily | As per specialist | Higher dose may be needed for TSH suppression |
Always follow dosing instructions from your doctor, who will adjust your treatment based on blood tests and symptoms.
Safety Profile and Side Effects
At the correct dose, Levothyroxine is very safe and most people experience few or no side effects. Problems are usually linked to doses being too high or too low.
| Common (May Affect >1/100) | Rare/Serious | Warnings |
|---|---|---|
| - Headache, nervousness - Insomnia - Sweating - Weight loss - Palpitations - Diarrhoea - Cramps - Feeling shaky | - Allergic reactions (rash, swelling, severe itching) - Cardiac arrhythmias (irregular heart beat) - Chest pain (angina) - Severe hypertension - Seizures (extremely rare) | - If you develop chest pain, severe headache, unusual heart beats, or a rash, seek medical help immediately. - If pregnant, dose adjustment is often needed—inform your healthcare provider. - Elderly and those with heart disease require extra care. |
Guidelines for Proper Use in Australia
- Keep Levothyroxine in its original packaging and store below 25°C, away from light and moisture.
- Never share your medication with others.
- Order repeat prescriptions through your local pharmacy ahead of time to avoid running out.
- If you miss a dose, take it as soon as you remember (unless it’s almost time for your next dose—then skip the missed dose and continue as normal).
- Inform your GP and pharmacist about all medicines, supplements, or herbal products you use.
Alternative Treatment Options
- Natural Thyroid Extract (NTE—desiccated thyroid): Not routinely used in Australia, and not PBS subsidised; variable potency, less predictable response.
- Liothyronine (T3): Sometimes used in combination with Levothyroxine for specific patients, but not standard first-line; increased risk of side effects; not PBS-reimbursed except specialist use.
- Other medications: Newer combination products exist but are rarely needed and not routinely available.
- Non-medicinal options: Not medically appropriate—lifestyle changes and dietary adjustments cannot replace thyroid hormone for hypothyroid patients.
For nearly all Australians, Levothyroxine is the safest, most practical, and cost-effective first choice.
Legal, Registration, and Reimbursement Status in Australia
- Registered with the Therapeutic Goods Administration (TGA).
- Prescription Only (Schedule 4, S4).
- Listed under Pharmaceutical Benefits Scheme (PBS) for eligible patients—reimbursement allows affordable access.
- Available in all Australian states and territories through community and hospital pharmacies.
Recent Research and Clinical Guidance (2022–2025)
- Royal Australian College of General Practitioners (RACGP) guidance (2023): Emphasises individualised dosing based on TSH and FT4, with more cautious titration in elderly and cardiac patients.
- Endocrine Society and NICE (UK) guidelines: Affirm Levothyroxine as first-line for all forms of hypothyroidism. Regular review of therapy recommended every 12 months once target thyroid function is stable.
- Recent large studies (Jansen et al., 2022; Pearce, 2023): Confirm that carefully titrated Levothyroxine improves quality of life and cardiovascular outcomes in overt hypothyroidism. No benefit found for symptom-only, biochemically euthyroid patients.
- Combination T3/T4 (Liothyronine/Levothyroxine) therapy shows no added benefit for most patients, except in rare genetic deiodinase deficiencies (Stuebe et al., 2024).
- Pregnancy: New research supports regular dose adjustment and TSH monitoring every 4–6 weeks to maintain maternal and foetal health (RACGP, 2024).
Availability and Delivery in Australia
| Brand | Common Pack Sizes | Typical PBS Price (2024) | Indicative Express Delivery (Sydney/Melbourne/Brisbane) |
|---|---|---|---|
| Eutroxsig® | 200 tablets (50 mcg, 100 mcg) | $7.30 (concession), $30.60 (general) | Next-day (capital cities), 2–3 days (regional/rural) |
| Oroxine® | 200 tablets (25–200 mcg) | $7.30 (concession), $30.60 (general) | Next-day, 2–3 days regional/rural |
| Eltroxin® | 100, 200 tablets | $7.30/$30.60 | Next-day |
For urgent supply, ask about in-pharmacy express pick-up or direct-to-door delivery options.
FAQ – Your Questions Answered
- 1. What should I do if I miss a dose?
Take your missed dose as soon as you remember, unless it is nearly time for your next dose. Do not double up. If unsure, check with your pharmacist. - 2. Do I need regular blood tests while taking Levothyroxine?
Yes—TSH and FT4 are monitored every 6–8 weeks during dose adjustment, and every 6–12 months once stable. - 3. Can I switch between different brands or generics?
It’s best to stay on the same brand, as absorption can vary slightly. If you do switch, tell your doctor or pharmacist, and monitor your thyroid function as recommended. - 4. Will Levothyroxine help me lose weight or improve mental health?
No—Levothyroxine only replaces thyroid hormone in deficiency. Taking more than you need can be dangerous and is not recommended. - 5. Can I take Levothyroxine during pregnancy or breastfeeding?
Yes—safe and needed in most cases, but your dose may require adjustment. Always inform your doctor if you are planning pregnancy, pregnant, or breastfeeding.
Contact and More Information
If you have further questions, speak to your local community pharmacist, GP, or specialist endocrinologist. For TGA safety updates or PBS coverage enquiries, visit www.tga.gov.au or www.pbs.gov.au.
