Iodine is needed to make thyroid hormones, which support metabolism, growth and brain development. Most people only need a small amount, but both too little and too much can cause problems. In the UK, milk, yoghurt, white fish and eggs are useful sources, and some plant milks are fortified. Labels are worth checking because fortification varies.
People who avoid dairy and fish may need to pay closer attention, particularly when planning a pregnancy or while pregnant. Seaweed is unpredictable: some products contain very high amounts of iodine, so it is not a safe way to guess at a daily dose. A pharmacist, GP or dietitian can advise if your usual diet contains few reliable sources.
Thyroid disease and medicines such as amiodarone make individual advice especially important. Don't start an iodine supplement to treat tiredness or weight change without discussing those symptoms with a clinician, as they have many possible causes.
This article offers general information and does not replace advice from someone who knows your medical history. If you are pregnant, take regular medicine or live with a long-term condition, speak to your GP, nurse, pharmacist or a registered dietitian before making a major change to the way you eat.
Where iodine hides in a normal shop
Milk and yoghurt are important iodine sources in many UK diets, while white fish and eggs also contribute. Some plant drinks and breakfast cereals are fortified, but amounts vary, so check the label on the product you actually use.
UK table salt is not routinely iodised, and increasing salt is not a sensible iodine strategy. Vegan diets without fortified alternatives may need advice from a registered dietitian.
Pregnancy and breastfeeding
Iodine is especially important during pregnancy and breastfeeding because it supports thyroid hormone production and early brain development. UK guidance does not set a separate higher intake target, but people who avoid major iodine sources may need individual dietary advice.
Follow current advice from your midwife, GP or dietitian when choosing a supplement. Avoid kelp products because their iodine content can be very high and unpredictable.
Low intake is more likely when dairy, fish and fortified alternatives are all absent. Tiredness, weight change and other possible thyroid symptoms are non-specific and need blood tests rather than self-diagnosis.
Normal portions of cooked broccoli and other brassicas are not a practical iodine problem for most people. Existing thyroid disease or thyroid medicine makes individual advice more important.
An occasional sheet of nori is different from a daily kelp tablet. Iodine content varies widely between seaweeds, and excess intake can cause either overactive or underactive thyroid problems.
Treat seaweed as an occasional food unless a specialist has advised otherwise. Reliable ordinary sources and fortified foods are easier to use safely.
Budget meals that carry iodine
Fish pie, eggs on toast, yoghurt with fruit and fortified cereal are familiar ways to include iodine. Check fortification on plant alternatives rather than assuming every carton contains it.
Vary fish choices and follow current pregnancy advice about tuna and higher-mercury species. Planning fish and egg meals also helps prevent a suitable ingredient being bought without a clear use.
Plan with your midwife and the journal library
Bring your usual diet, allergies, cultural foods and supplements to pre-conception or antenatal appointments. A dietitian referral can help when several foods are excluded.
Neck swelling, a racing or irregular heartbeat, marked weight change or severe unexplained fatigue deserves clinical assessment. Adjusting iodine without testing can make some thyroid problems worse.