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Iron and Ferritin Deficiency

Hypothyroidism or underactive thyroid can lead to poor iron absorption which is why it’s important to check your iron and ferritin levels.

What causes iron deficiency?

Iron deficiency is caused by a lack of iron in the body which in turn causes iron deficiency anaemia.  It can be caused by dietary lack of iron, blood loss (i.e. stomach bleeding due to use of taking non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and aspirin and stomach ulcers; heavy periods, pregnancy and certain health conditions.1

What are the symptoms of iron deficiency anaemia?

The symptoms of iron deficiency are1:

    • tiredness and lack of energy

    • shortness of breath

    • noticeable heartbeats (heart palpitations)

    • pale skin

    • headaches2

    • hearing ringing, buzzing or hissing noises inside your head (tinnitus)

    • food tasting strange

    • feeling itchy

    • a sore tongue

    • hair loss – you notice more hair coming out when brushing or washing it

    • wanting to eat non-food items (for example, paper or ice) – called pica

    • finding it hard to swallow (dysphagia)

    • painful open sores (ulcers) in the corners of your mouth

    • spoon-shaped nails

    • restless legs syndrome

Also, iron and immunity are closely linked and therefore if you have low iron levels it may affect your immune system. 3 However, symptoms may depend on the severity of your iron deficiency.


Anaemia, due to a severe iron deficiency, will show up as low haemoglobin and hematocrit (percentage of red cells in the blood) when a complete blood count (CBC) test is carried out.1


If you are found to be iron deficient your doctor will prescribe a course of iron tablets that will be stronger than those available in your local chemist.

Iron tablets should not be taken at the same time as levothyroxine.11   Allow at least four hours after taking iron before taking your thyroid medication.

The recommended daily dose of iron is4:

    • men over 18 – 8.7mg a day

    • women aged 19-50 years -14.8mg a day

    • women over 50 – 8.7mg a day

The oral dose of elemental iron (the part of the tablet that is absorbable) for iron-deficiency anaemia should be 100 to 200 mg daily5.

There are several varieties of iron medications including ferrous sulphate, ferrous gluconate, and ferrous fumarate.6

The cheapest form of iron is ferrous sulphate, which can be obtained over the counter, but this needs to be taken in conjunction with food, a good vitamin E supplement since there is evidence that ferrous sulphate depletes this, and magnesium.  However, this preparation is often poorly tolerated.  Iron tablets can cause you to be constipated, have stomach pain, heartburn or feel sick.  They can also make your stools turn black.1

Ferrous gluconate may cause fewer side effects and is easier on the stomach.  There is also ferrous fumarate but this may not be any better tolerated than ferrous sulphate.6

Your doctor will make the decision on which to prescribe and, if it is not tolerated, he will change to another type of iron medication.

Animal-based liquid iron (heme) can blacken your teeth – this unfortunate side effect can be avoided by instead taking vegetable-based (non-heme) liquid iron.7 To counteract these symptoms, consider taking the tablets with or soon after your food and increasing the fibre and fluids in your diet.1 Taking vitamin C can assist the absorption of iron8,9  so at the very least wash your iron tablets down with orange juice.

Once you have finished your course of iron tablets you need to be aware that if your symptoms return you need to revisit your doctor for further testing. It should be noted that it could take many weeks, even months, to improve your levels, and it may be necessary to continue taking iron supplements to maintain those levels.1

Taking very high doses of iron can be fatal, particularly if taken by children.1

How to help yourself

If your iron deficiency is due to your diet try eating more dark green leafy vegetables and curly kale; cereals and bread with extra iron in them (fortified); meat – especially liver (if you are not a vegetarian); eggs; pulses (beans, peas and lentils); nuts and dried fruit.  You should be careful when eating wholegrain cereals with high levels of phytic acid as these can stop your body absorbing iron from other foods and pills.1

Some drinks can inhibit the absorption of iron such as tea, coffee, cocoa, milk and dairy so try not to have too much of these.1

What is ferritin?

Ferritin is a protein that combines with iron and is used by the body as its main form of iron storage.  If you are losing iron, the body can maintain its iron levels by drawing on its stores until they are all used up.  When this happens, the iron levels can no longer be maintained at their normal levels and will start to fall.  Eventually, anaemia – a deficiency in either the quality or the quantity of blood – will develop.12

However, ferritin levels can fall before iron levels themselves fall: low ferritin levels, therefore, indicate that intervention is needed to prevent the usually symptomless slide into anaemia.

The normal range of ferritin can be anywhere between 15 and 400 mg/dL,13 (lab ranges can vary).  Many healthcare practitioners think that iron supplementation should be considered by anyone with ferritin levels below 60 mg/dL with the aim of treatment to raise ferritin levels to within 70 to 90 mg/dL. If you have low ferritin levels, consider including iron-rich foods in your diet.

Interestingly, high ferritin has a link with inflammation and cell stress and damage.14, 15

Hypothyroidism can lead to reduced levels of hydrochloric acid in the stomach (as can anti-acid medications) leading in turn to poor iron absorption.16

Hypothyroidism can also result in lowered body temperature causing fewer red blood cells to be produced by the temperature-sensitive bone marrow.

Low iron/ferritin levels are a particular problem for those with hypothyroidism for several reasons.

Firstly, normal thyroid hormone metabolism depends on adequate supplies of iron, together with iodine, selenium and zinc.17

Secondly, symptoms of anaemia mimic those of hypothyroidism so causing the patient to believe they are not taking enough thyroid medication or that the thyroid medication they are taking is not working.1

For example, hair loss is a sign of hypothyroidism but it is also caused by low iron levels.18,19  Patients can easily believe that they have this as a remaining sign of hypothyroidism without realising they may have low levels of iron/ferritin. It is very important that all hypothyroid patients also get tested for iron/ferritin.

Thirdly, low iron levels may result in the thyroid peroxidase enzyme, which is iron-dependent, becoming less active so reducing the production of thyroid hormones.  The thyroid metabolism may also be altered, the conversion of T4 (thyroxine) into T3 (triiodothyronine) slowed down, and the binding of T3 modified.  The circulating levels of TSH (thyroid-stimulating hormone) may also be increased.20,21

Also, in patients with subclinical hypothyroidism and anaemia, levothyroxine treatment may help.22

You can now see how important it is for patients with hypothyroidism to check their iron and ferritin levels as being deficient in this very important mineral can cause problems for these patients.23,24,25,26

For more support check out our online community:


  1. Iron deficiency anaemia
  2. Is iron-deficiency anaemia associated with migraine? Is there a role for anxiety and depression?
    Pamuk GE, Top MŞ, Uyanık MŞ, Köker H, Akker M, Ak R, Yürekli ÖA, Çelik Y, Wien Klin Wochenschr. 2016 Dec;128(Suppl 8):576-580.
  3. Iron and the immune system.
  4. Vitamins and minerals
  5. Anaemia, iron deficiency
  6. Anaemia – iron deficiency!scenario
  7. Iron supplement
  8. The role of vitamin C in iron absorption.
  9. Taking Iron Supplements – Information for patients (vitamin C)
    Oxford University Hospitals NHS Trust
  10. Ferrous sulphate reduces thyroxine efficacy in patients with hypothyroidism.
    Norman R. C. Campbell, MD; Brian B. Hasinoff, PhD; Helga Stalts, RN; Babu Rao, MD; Norman C. W. Wong, MD,
    Ann Intern Med. 1992; 117:1010-3
  11. British National Formulary (BNF),by%20at%20least%204%20hours
  12. Anaemia, iron deficiency
  13. Ferritin ology/tests/Ferritin/
  14. Acute-phase Proteins, CRP, ESR and Viscosity
  15. Serum ferritin is an important inflammatory disease marker, as it is mainly a leakage product from damaged cells.
  16. Diet
  17. The relationship between iron status and thyroid hormone concentration in iron-deficient adolescent Iranian girls.
  18. Iron Plays a Certain Role in Patterned Hair Loss
  19. Iron status in diffuse telogen hair loss among women
  20. The Impact of Iron and Selenium Deficiencies on Iodine and Thyroid Metabolism: Biochemistry and Relevance to Public Health
    Michael B. Zimmermann and Josef Köhrle.
    Thyroid. July 2004, 12(10): 867-878.
  21. Association Between Serum Ferritin and Thyroid Hormone Profile in Hypothyroidism  Ashuma Sachdeva, Veena Singh, Isha Malik, Prasanta Saha Roy, Himanshu Madaan, Rajesh Nair.
    Int J Med Sci Public Health2015; 4(6): 863-865
  22. Hematologic Effects of Levothyroxine in Iron-Deficient Subclinical
    Hakan Cinemre; Cemil Bilir; Feyzi Gokosmanoglu; Talat Bahcebasi
  23. Serum ferritin as a marker of thyroid hormone action on peripheral tissues
    Takamatsu J, Majima M, Miki K, Kuma K, Mozai T.
    J Clin Endocrinol Metab. 1985 Oct;61(4):672-6.
  24. Thyroid profile and iron metabolism: mutual relationship in hypothyroidism
    Kiran Dahiya, Monica Verma, Rakesh Dhankhar, Veena Singh Ghalaut, PS Ghalaut, Ashuma Sachdeva, Isha Malik, Rajesh Kumar
    Biomedical Research 2016; 27 (4): 1212-1215
  25. Thyroid Hormone Modulates the Interaction between Iron Regulatory Proteins and the Ferritin mRNA Iron-responsive Element
    Peter J. Leedman; Adam R. Stein; William W. Chin; Jack T. Rogers
    Journal of Biological Chemistry
  26. Iron Metabolism in Patients with Impaired Thyroid Function
    Ayhan ONAT, Aymelek GÖNENÇ, Safa GÜRCAN, Meral TORUN
    J. Fac. Pharm, Ankara 32 (4) 221-230,2003

Date updated: 09.09.22 (V1.5)
Review date: 31.01.23

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