Is your iodine level affecting your health?

Too much or too little iodine can have a negative impact on your health. Are you getting the right amount?

Iodine is a mineral that can be immensely underrated. It’s vital for thyroid health, but evidence suggests that many of us don’t get enough in our diets [1]. And more evidence is emerging to suggest that changes to the way food is made and the diets we choose are increasing our likelihood of developing an iodine deficiency [2]. 

On the other hand, too much iodine can be harmful. So, how can you get it right?  

In this blog we discuss: 

What is iodine?

Iodine is one of the most important minerals for thyroid health. The thyroid is a butterfly-shaped gland that sits in the neck and produces thyroid hormones. Thyroid hormones travel around the body and regulate every single process, from your heartbeat to your metabolism. 

Iodine is essential for thyroid health because it’s a vital component of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3). Without enough iodine, our bodies cannot make these hormones, so they cannot carry out essential roles in the body. 

Iodine-rich foods

Current recommendations say that adults need 140 μg of iodine a day to stay healthy [3]. This is a tiny amount, so it’s easy to get enough if you eat the right foods regularly. 

Iodine-rich foods include [4]: 

  • Shellfish 
  • Fish 
  • Eggs 
  • Milk and cheese 
  • Iodine-fortified plant milk 
  • Iodine-fortified salt 
  • Seaweed 

Symptoms of an iodine deficiency

Symptoms of an iodine deficiency can range from very mild to very severe. Experts have put together a term to cover the whole spectrum of iodine deficiency: iodine deficiency disorders (IDD). 

A low intake of iodine means your thyroid gland has to work harder, and this can produce a swelling in the neck, known as a goitre. A mild deficiency during pregnancy or in childhood, could cause a lower IQ or impact reading ability in the growing child in later life [5]. 

Symptoms of an iodine deficiency differ from person to person but may include: 

  • A goitre or neck swelling 
  • Cognitive problems, such as difficulty concentrating 
  • Low work productivity 

Iodine deficiencies and thyroid conditions

As iodine is important for your thyroid health, low levels of iodine can affect how well your thyroid gland works. If you have a long-term iodine deficiency, you may develop a thyroid condition such as hyper- or hypothyroidism [6].  

Symptoms of thyroid conditions include: 

  • Tiredness or muscle weakness 
  • Depression or other changes to your mood 
  • Difficulty regulating body temperature (being too hot or too cold) 
  • Abnormally slow or fast movement and thoughts 
  • Changes to the menstrual cycle 
  • Loss of libido (sex drive) 
  • Bodyweight changes, such as weight loss or weight gain 

You can find more information on thyroid health and necessary nutrients in our Thyroid Guide.  

Are you at risk of an iodine deficiency?

Though iodine deficiency is reasonably rare, you can be more at risk of a deficiency if: 

  • You don’t have a healthy balanced diet that includes iodine 
  • You are a premenopausal or pregnant woman  
  • You are a vegan  

In the past, iodine deficiency was a major problem because people relied on the food they grew to eat. If the soil was low in iodine, this would mean foods were also low in iodine. 

Food is now readily available from all over the world, so the severe form of iodine deficiency is now very rare in the UK. But there is growing concern that many people are living with milder deficiencies, which do not always have obvious symptoms. 

Many countries, such as New Zealand and the United States, have iodine fortification programmes. This means that iodine is added to some foods, such as salt and bread, to keep the population healthy. The UK does not currently have an iodine fortification programme. 

Your risk of iodine deficiency as a woman

Many teenage girls and young women in the UK may not get enough iodine in their diets [1]. Pregnant women are also at increased risk of iodine deficiency. Their needs are greater as they create more thyroid hormones and provide iodine to the baby [7]. A large study found that amongst pregnant women, a mild-moderate iodine deficiency was associated with a higher prevalence of preeclampsia or pre-term labour [8]. Women need iodine from the early pregnancy stages, so you should ensure you’re getting enough iodine in your diet for many months before getting pregnant. 

Your risk of iodine deficiency as a vegan

If you avoid dairy products (because of an allergy, intolerance, or diet), you could be at risk of iodine deficiency [9]. New research also suggests that people who follow a vegan diet are at higher risk of a deficiency – so vegans should look for fortified food products. You can read more about vegan nutrition in our blog: plant-based diets and nutrition

Should I take an iodine supplement?

Like many nutrients, iodine can be harmful both in deficiency (too little) and excess (too much). Supplementation can mean you’re at a higher risk of having far too much iodine. Many supplements that seem harmless and natural (such as iodine-containing seaweed supplements) may be inconsistent in their iodine content. So, how can you be sure how much iodine you are putting into your body? 

The answer is that you can't be sure without measuring your levels. It’s a much safer (and cheaper) approach to increase your intake of iodine-containing foods.  

Before you consider taking iodine supplements, it’s best to discuss this with your doctor, as taking too much iodine can be harmful [10].  


  1. The Lancet Diabetes & Endocrinology (2016) “Iodine deficiency in the UK: Grabbing the low-hanging fruit,” The Lancet Diabetes & Endocrinology, 4(6), p. 469. Available at:
  2. Hatch-McChesney, A. and Lieberman, H.R. (2022) “Iodine and iodine deficiency: A comprehensive review of a re-emerging issue,” Nutrients, 14(17), p. 3474. Available at:
  3. (no date) NHS choices. NHS. Available at: (Accessed: January 23, 2023). 
  4. Iodine (2021) The Nutrition Source. Available at: (Accessed: January 23, 2023). 
  5. Leung, A.M. and Brent, G.A. (2013) “Children of mothers with iodine deficiency during pregnancy are more likely to have lower verbal IQ and reading scores at 8–9 years of age,” Evidence Based Nursing, 17(3), pp. 86–86. Available at:
  6. Chung, H.R. (2014) “Iodine and thyroid function,” Annals of Pediatric Endocrinology & Metabolism, 19(1), p. 8. Available at:
  7. Pearce, E.N. (2015) “Iodine deficiency in pregnant women in the UK: The costs of inaction,” The Lancet Diabetes & Endocrinology, 3(9), pp. 671–672. Available at:
  8. Abel, M.H. et al. (2020) “Insufficient maternal iodine intake is associated with subfecundity, reduced foetal growth, and adverse pregnancy outcomes in the Norwegian mother, father and child cohort study,” BMC Medicine, 18(1). Available at:
  9. Office for Health Improvement and Disparities (2021) Iodine: Migrant health guideGOV.UK. GOV.UK. Available at:,consider%20a%20supplement%20containing%20iodine. (Accessed: January 23, 2023). 
  10. (no date) NHS choices. NHS. Available at: (Accessed: January 23, 2023). 


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