Low-Iodine Diet: A Practical Guide
A low-iodine diet is sometimes recommended for one to two weeks before radioactive iodine treatment or scanning. Reducing iodine intake helps the thyroid take up the radioactive iodine more effectively.
The exact duration and instructions vary between centres — always follow your treating team’s advice.
Last medically reviewed: 15 November 2025
Key points
- A low-iodine diet is used before radioactive iodine treatment or scans.
- It is usually followed for one to two weeks.
- Avoid iodised salt, seafood, seaweed and iodine supplements.
- Follow your treating team’s specific instructions.
Why it is used
The thyroid takes up iodine avidly. If the body is saturated with ordinary iodine, radioactive iodine is diluted and less effective. A low-iodine diet reduces that competition.
It is used mainly before radioactive iodine for thyroid cancer and sometimes before a scan.
What to avoid
Avoid iodised salt and salty processed foods, seafood and seaweed, dairy products in large amounts, egg yolks, and iodine-containing supplements or cough medicines. Some breads and restaurant foods contain iodised salt.
Check labels for iodine and avoid kelp or seaweed products.
What to eat
Fresh fruits and vegetables, fresh meat and poultry, rice, pasta, potatoes, beans, unsalted nuts and home-cooked meals made without iodised salt are generally suitable.
Use non-iodised salt if needed, and drink water rather than iodine-rich beverages.
Practical tips
Plan meals at home, read labels, and ask family members to help. The diet is temporary and not a permanent restriction. Ask your team for a written list, as recommendations vary.
When to seek urgent medical help
- Severe weakness, dizziness or fainting while dieting.
- Unintentional significant weight loss.
- Symptoms of low blood sugar or dehydration.
This guidance does not replace emergency services. If you are seriously unwell, seek urgent medical care immediately.
Frequently asked questions
How long do I need the diet?
Usually one to two weeks before treatment, depending on your centre’s protocol. Follow the instructions you are given.
Can I use normal salt?
Avoid iodised salt during the diet. Use non-iodised salt if your team permits it.
Is the diet dangerous?
It is temporary and generally safe for most people, but ask your team if you have other dietary or medical conditions.
References & further reading
This page is based on established medical knowledge and guidelines from authoritative sources. Always consult a qualified clinician for personal medical advice.
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