Confused about Iron supplements


I just read on the Thyroid UK website that iron supplements hinder the absorption of Levothyroxine.

But I've also read and heard through this site that Ferritin levels need to be good in order to Levothyroxine to work properly.

Needless to say, I am now a bit confused. And for once, it's not due to brain fog! Can anyone shed light on these apparent contradictions?

Thank you :)

29 Replies

  • Iron has to be taken 4 hours away from your thyroid meds. Prior to that and you have absorption issues.

  • Does this apply also to T3?

    I have always assumed so but confirmation would be helpful.

  • I take it that it applies to T3 & NDT. I avoid any other supplements for >4 hours.

  • I may be wrong but I don't think it applies to T3 as it's the conversion that it affects and T3 is already in a converted form.

  • You are right that iron is important for conversion, but the four hour rule is based on this:

    Levothyroxine binds to iron and iron compounds in the gut to form a purple, stable complex. That complex passes straight through. Technically, the iron that binds to the levothyroxine is also unavailable but we might be talking about 65 milligrams of elemental iron against, say, 100 micrograms of levothyroxine. An order of magnitude more iron being taken. The difference it makes to iron is probably less that the difference between tablets. The difference it can make to levothyroxine is very significant.

    Unfortunately, there has been far too little research on interactions between liothyronine and anything else, especially in the stomach and gut. So we end up making what could be a really misleading assumption - that levothyroxine and liothyronine are similarly affected.

  • Thank you. Excellent answer. I suppose, in the absence of evidence to the contrary, that it makes sense to keep iron and t3 apart. I also wondered -while your here 😉- whether liquid iron drops is absorbed faster than solid pills and if so, do we know if this is relevant for T4 takers?

  • Afraid I don't know! I suspect there will be more than enough iron to bind levothyroxine regardless how efficiently the iron supplement is absorbed. But that is a guess.

  • I would have guessed so as I know that liquid/gel vitamin D capsules are the ones you want for absorption.

    Needless to say my gp just switched mine to solid form, cheaper! I shall be having words. Haha

  • Thank you Leverette. I am sometimes a bit slap dash about timings...will pay more attention.

  • If you're low on iron then it's likely you've been low in B12 (methylcobalamin) too. B12 deficiencies are masked by relatively high folate levels (given our diets often have folic acid fortified foods) and the B12 problem doesn't get picked up on for years until we start getting terrible neurological symptoms. B12 is indirectly responsible for raising iron levels in the blood as it helps replace lost blood cells.

    I watched the video posted by Shaws yesterday about B12 and it was a real eye opener.

    I always take B12 with breakfast and would recommend taking iron later on with an orange / vitamin C. Also best to avoid tea and dairy around the time you take iron.

  • Not necessarily - while most posters who have Hasimotos tend to have wide spectrum nutrient problems not everyone with hypothyroidism does.

    Regardless you should always test your levels before starting a supplement regime.

  • How should we be checking our B12, because there is a wealth of evidence that simple blood tests alone are inadequate?

  • By signs AND symptoms AND blood tests. People know that when they don't feel right.

    There are some posters here who have posted blood test results where they have very low levels in one nutrient but others are high in range and they state they don't supplement.

    Also as people are already taking a load of medication plus supplements it can be confusing, stressful and expensive to have to add another supplement to your regime.

  • It's not an expensive thing to supplement though and the effects of not supplementing a far more costly - days off work, elderly people falling over and breaking their hips...

    I think it's a pretty tough ask to expect people to wait until it shows up in their blood although it makes for a more 'elegant' scientific result. People are not lab rats, after all.

  • The problem is if we say supplement without them having had a test but they actually need B12 injections then they won't get them as a follow up a B12 test maybe be skewed.

    Remember NHS doctors go on blood tests and people don't always know when they are going to have one.

  • Sorry, was just assuming that the test was already done alongside ferritin and FBC (maybe we have a surprisingly thorough endo).

    However, once you've had the initial test which says that your B12 is 'normal' and your GP is obviously going to be unwilling to offer B12 injections (even when you're showing some neuro symptoms which they just put down to thyroid), that, under these circumstances that it'd be advisable to supplement anyway for a trial period to see if symptoms improve.

    A relative has been on levo for 2 years, keeps falling over, can't feel her own feet, has tinnitus, can't remember our names etc. but because her B12 is in the 'normal' range her GP will do nothing for her... unfortunately, because she is an elderly 'disciple' of her GP she won't listen to anyone else.

  • If you have normocytic anaemia taking iron is dangerous, optimum thyroid meds needed.

  • There are a few blood disorders where taking iron is dangerous which is why posters are commonly asked not only about their ferritin level but whether they have had a full blood count and know their haemoglobin level.

    I've also noticed that female posters then tend to reveal whether they have any other blood disorders themselves or in their blood-relations, but male posters have to be specifically asked for this information.

  • Yes iron can be a problem but I get over it by taking thyroxine before bedtime and the rest of the stuff I need throughout the day.

  • You need to establish a daily routine. For example I take my levothyroxing first thing in the morning upon waking. Followed a few hours later by B12 and 2 hours later by Iron. This spacing apart facilitates individual absorption. I don't eat before about 12 noon (I'm not hungry due to sluggish metabolism plus I'm at the gym until around 11am). My iron supplement has vitamin C in it to further improve absorption. The most important is to take your thyroid medication separately, early and allow plenty of Tim before adding food

  • Is it true that B12 can't be reliably blood tested if the patient is taking supplements? I heard that in order to get an accurate reading it is necessary to have been off it for a year.

  • It would be folly to avoid taking B12 for a whole year just so that a frankly primitive blood test would show up the deficiency - to be honest even that isn't necessarily a given, because folic acid can mask B12 deficiency by correcting the shape of macrocytic blood cells (which is what the tests are looking for).

    B12 deficiency is way more than a haematological issue - the signs of early B12 deficiency are neurological way before they show up in the blood!!!

    B12 can't be reliably tested from bloods only, period, therein lies the problem. I personally believe that it's generally better to assume that you need to trial taking B12 if you have any autoimmune issue (due to poor gut absorption) then watch if by taking it if symptoms improve. It is probably one of the safest supplements to take. My memory was dire before taking it - I'd needed it badly!


  • NICE guidelines state that for someone supplementing B12 they should be monitored by having a full blood count and a reticulocyte count once they have started supplementing as this shows the effect on the blood cells.

    So by that you can conclude that the B12 test everyone gets is either inadequate or more expensive. However as they state test vitamin B12 levels to make an initial diagnosis it is likely the former.

  • Hi Tracyd59,

    It can be very confusing. How I do mine is the way I was told. Basically do not take the two medications together. The iron will hinder the absorption of thyroid medication if taken together, same with the vitamin D supplement.

    Thyroid medication I take before food in the morning. Take my T3 first and then T4 about half an hour afterwards.

    Vitamin D = after lunch

    Iron = before I go to bed

    I always take my water medication about an hour after breakfast, unless I am going out. Then I take it later. The medication does not work everyday depends on fluid retention, but when it does work, I am constantly going to the loo. Which is and can be a pain in the rear!

    I bought myself a dosette box to remind me as well.

    Hope this helps :)

  • Thanks Jollydolly. That makes sense. It's a minefield trying to get the timings etc right!

  • The GP didn't tell me, it was a pharmacist lol - I was practically taking it all together. So far regarding so good, now I have been told. Hope it helps you :)

  • Foods high in iron often are high in B12, which is why I suspect it may be relevant. Gastric atrophy can affect iron and B12 absorption.

    If your B12 levels were not checked alongside your iron then ask to have them checked!

    As bluebag has advised - don't supplement until you've got the result - then it's up to you to decide based on your symptoms......

    It's worth checking the symptoms of low B12 as there is a lot of crossover with hypothyroid.

  • Hello tracyd59,,,,I have to take both of these meds,,,so the iron goes down at night,(I used the liquid iron,spatone,it does not cause so many side effects),,and the levo goes down the first thing in the morning,,usually about 6-8 hours apart,,,and up to now things seem to be going along alright,,,,hope this helps you a little,,,,ttfn from karen.

  • thanks Karen!

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