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Levothyroxine: what to be careful with
Levothyroxine replaces the thyroid hormone the body is not making enough of, in an underactive thyroid.
General information only, and not exhaustive. This is not medical advice, not a full list of interactions, and not a reason to start, stop or change a medicine. Interactions depend on the exact drug, the dose, your other medicines and your own health — a pharmacist or doctor is the one who decides. Always read the leaflet that came with your medicine, and ask your pharmacist before adding anything, including supplements.
Group, not a brandATC H03AA01
Examples in this group: levothyroxine sodium (thyroxine, T4). Interactions usually belong to the whole group, but your own leaflet is brand-specific — always the final word.
Food and drink to be careful with
- Calcium and iron supplements. Both bind levothyroxine in the gut and can substantially reduce how much is absorbed. The usual practical answer is a gap of about four hours between them. This is one of the most consistently repeated instructions in the whole of medicine, and one of the most often missed.
- Coffee. Coffee taken at the same time reduces absorption measurably. The standard advice is to leave a gap between the tablet and the first coffee of the day.
- Soy products and high-fibre meals. Both reduce absorption. It is consistency that matters most: a stable soy or fibre intake can simply be part of the dose that gets adjusted to, whereas a sudden change shifts the level.
- Grapefruit juice. Reduces absorption modestly. Less important than calcium or iron, but it is in the leaflet.
Timing around meals
Levothyroxine is normally taken on an empty stomach, commonly thirty to sixty minutes before breakfast, or alternatively at bedtime at least a few hours after the last food. What matters most is doing the same thing every day, because the dose was set against that routine.
Alcohol
No direct interaction is described between alcohol and levothyroxine.
Other things to watch
- Proton pump inhibitors reduce stomach acid and can reduce levothyroxine absorption over time.
- Different brands and formulations are not always freely interchangeable; a switch is sometimes followed by a blood test.
- Pregnancy increases requirement, usually early and substantially, and is followed closely.
If anything here does not match what you were told, or you notice a new symptom after starting a medicine, contact your pharmacist or doctor — do not just stop taking it. Stopping some medicines suddenly is more dangerous than any food interaction.
Source: The product's own Summary of Product Characteristics and patient information leaflet, published per medicine by the licensing authority. The four-hour separation from calcium and iron appears in levothyroxine product information across markets. · checked 2026-09-02
Frequently asked questions
What should I avoid with levothyroxine?
Calcium and iron supplements is the one people ask about most: Both bind levothyroxine in the gut and can substantially reduce how much is absorbed. The usual practical answer is a gap of about four hours between them. This is one of the most consistently repeated instructions in the whole of medicine, and one of the most often missed. This is general information — your leaflet and pharmacist have the specifics.
Can I drink alcohol with levothyroxine?
No direct interaction is described between alcohol and levothyroxine.
Should levothyroxine be taken with food?
Levothyroxine is normally taken on an empty stomach, commonly thirty to sixty minutes before breakfast, or alternatively at bedtime at least a few hours after the last food. What matters most is doing the same thing every day, because the dose was set against that routine.
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All medicine groups · Alcohol units and clearance · Blood test reference ranges
Track meals and symptoms alongside your medicines
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