Why You Need Levothyroxine
If your thyroid gland is underactive (hypothyroidism), it does not produce enough thyroxine (T4). Levothyroxine is identical to the T4 your body should be making — it's not a "drug" but a hormone replacement.
Critical RuleAlways take levothyroxine on an empty stomach, 30–60 minutes BEFORE breakfast. Food, coffee, and calcium significantly reduce absorption by up to 40%.
TSH Target Ranges
| Patient Group | TSH Target |
|---|---|
| Most adults | 0.4–2.5 mU/L |
| Elderly (>65) | 1.0–4.0 mU/L (slightly higher is acceptable) |
| Pregnancy | 0.1–2.5 mU/L (1st trimester) |
| After thyroid cancer | <0.1 mU/L (suppressed — intentional) |
| Subclinical hypothyroidism | Discuss with doctor — not always treated |
Drugs That Reduce Levothyroxine Absorption
| Substance | Separation Needed |
|---|---|
| Calcium supplements | 4 hours apart |
| Iron supplements | 4 hours apart |
| Antacids (calcium carbonate) | 4 hours apart |
| PPIs (omeprazole etc.) | Take levothyroxine even earlier |
| Coffee / milk | 30–60 minutes minimum |
| Soya products | 4 hours apart |
Practical TipSet an alarm 45 minutes before your usual breakfast. Take your levothyroxine tablet immediately, then go back to sleep or have your coffee after 45 minutes. Consistency matters more than exact timing.
Symptoms of Too Little (Under-treatment)
- Persistent fatigue and sleepiness
- Weight gain despite dieting
- Feeling cold all the time
- Brain fog, poor concentration
- Depression
- Constipation
- Dry skin, hair loss
Symptoms of Too Much (Over-treatment)
- Heart palpitations
- Anxiety, tremor
- Weight loss
- Insomnia
- Diarrhoea
- Osteoporosis risk with prolonged over-treatment
Can I switch between brands of levothyroxine?
Not ideally. Different brands may have slightly different bioavailability. If you must switch, get a TSH check 6 weeks later.
I feel better on T3/T4 combination — is this valid?
Some patients do better on combination therapy (levothyroxine + liothyronine). Discuss with an endocrinologist if you have persistent symptoms despite normal TSH.
Does levothyroxine cause weight loss?
Normalising thyroid hormone may help you lose weight gained due to hypothyroidism, but it is not a weight-loss drug and shouldn't be taken for that purpose.
How long until I feel better?
Most people notice improvement within 2–4 weeks, but full benefit can take 3–6 months as TSH stabilises.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.