Know this first: side effects of taking too much
Iodine is not a "more is better" nutrient. High doses can cause:
- Nausea or vomiting, and changes in taste like a metallic taste in your mouth
- Headache, dizziness, diarrhea
- Heart palpitations, dry mouth
- Extra saliva and bleeding gums
- Hives, or swelling of the eyes or lips (allergic reaction)
If you get these symptoms, stop right away. If your eyes or lips swell or you feel short of breath, get medical care immediately.
Iodine daily recommendation and upper limit
| Category | Amount |
|---|---|
| Daily recommendation (adults) | 150 mcg |
| Daily upper limit (US standard) | 1,100 mcg |
| Daily upper limit (some other countries' standards) | 2,400 mcg |
mcg (microgram) is one-thousandth of a mg. Always check the unit on the label.
If you often eat seaweed like nori, kelp or seaweed soup, you already get a fair amount of iodine from food alone. So it's best to avoid megadoses (far more than the recommended amount). If you take a supplement, take it after a meal.
Signs of low iodine: get a blood test first
When you're low on iodine, your body makes less thyroid hormone. That slows your whole system down and can cause symptoms like these:
- □ You swell easily and have gained weight
- □ You feel cold more than other people
- □ Your skin is dry
- □ You're forgetful
- □ Your periods are irregular
- □ You're always tired and have cold hands and feet
According to World Health Organization data, about 20% of adults and about 30% of school-age children are low in iodine. Many women look into iodine because of fatigue, cold hands and feet, or weight gain.
Talk to your doctor first if
- You have a thyroid condition or take thyroid medication: iodine can throw off your thyroid levels. Talk to your doctor first.
- You eat seaweed often: adding a supplement could push you too high.
- You take a multivitamin: many already contain iodine. Check the label so you don't double up.
Medications and conditions to watch
- Caution Thyroid medication (during thyroid treatment) — Can throw off thyroid levels — talk to your doctor before taking it
- Note Multivitamin — Many multivitamins also contain iodine — check the label so you don't double up
Combinations
Works well with: Selenium
Want it in one pill with others? Compare prenatal vitamins →
Frequently asked questions
How much iodine do I need a day?
Adults need 150 mcg a day. The upper limit is 1,100 mcg in the US (2,400 mcg by some other countries' standards), so avoid high-dose products.
What happens if you take too much iodine?
You may get nausea, a metallic taste, headaches, diarrhea, heart palpitations or bleeding gums. If you have an allergic reaction with swelling of the eyes or lips, get medical care right away.
If I eat a lot of seaweed, do I still need an iodine supplement?
If you often eat seaweed like nori or kelp, you probably don't need extra. Adding a supplement could actually push you too high.
Should I take iodine for hypothyroid symptoms?
If swelling, feeling cold, fatigue and weight gain keep coming back, get a thyroid blood test before trying a supplement. Depending on the cause, iodine may not be right for you.
Can I take iodine with selenium?
Yes. Some say selenium eases the strain on the thyroid when iodine is high, so they're often mentioned together. Still, avoid taking a lot of iodine itself.
Related concerns
Last updated 2026-10-12