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Thyroid UK
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Unpleasant side effect of Ferrous Fumarate?

GP blood tests showed that I was quite anaemic, and I was put on Ferrous Fumarate, 3 tablets a day. Apologies if this is TMI, but over the last few months, my wee has had a really strong sour smell, although I have no symptoms of urine infection. There is nothing in the information leaflet to suggest this is a side effect, and the Pharmacist at Boots wasn't aware of it. Havent been to the GP yet, but just wondered if anyone else has experienced this?

Just as an aside, my GP thinks the anaemia might be due to internal bleeding and I recently had to undergo a very traumatic endoscopy, which showed nothing untoward. I on the other hand think it's one of many symptoms of a thyroid issue, but she is not interested because my TSH is 'normal'.

I did post my last GP blood results from October and Blue Horizon results from January, and advice from members suggest that I am heading towards a thyroid issue. Planning to test again soon so will be interesting to see if things have changed.

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I'm always on iron pills lol but I can say I've never experienced this side effect. My stomach yes, but not my bladder. Are you taking any other meds and drinking enough water - increase this anyway when taking iron as can cause constipation?

Some other supplements change my urine especially the B Vits. Otherwise check for urinary tract/bacterial infections anyway as sometimes symptomless etc. High blood sugar levels can cause changes to smell but is normally a sweet smell,

Some foods can change the smell too so have you started eating things you didn't before - sugar puffs always made my wee smell funny before I gave up gluten - have no idea why this particular food item did this mind you lmao :-)


I've got a feeeling I had something similar when I was on Mercury Pharma ferrous fumarate a year or so ago, but I didn't really take much notice. I'm not seeing (smelling?!) it with a different brand, so perhaps fillers in something you are taking.

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Aha! Likewise I have been on FF before and never experienced this, but I have just checked the pack and lo and behold, it is MercuryPharma! I will have a word with the pharmacy at Boots to see if I can try a different brand - thank you!


Thanks for your suggestions. Everything else is just the same - no change in meds or supplements, and this occurs everyday, strongest first thing in the morning, so not related to any particular food. Also, I am diabetic, so recognise the sweet smell you describe if my blood sugar is high.

Yes, its funny how different foods can affect your wee - apparently asparagus can be especially vile!!

However - it looks like Angel_of_the_North may have cracked it with the suggestion that it could be fillers in the particular brand of FF tablets, so I will investigate that.

Thanks again!


lol Well you always try and sweeten it up somehow if it bugs you lol - I always found mine sweeter if had the 1000mcg Vit C Effervescent tabs lol!

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Worth a try! :-)


Just as an aside, my GP thinks the anaemia might be due to internal bleeding and I recently had to undergo a very traumatic endoscopy, which showed nothing untoward.

Endoscopy is worth doing if someone has a gastro-intestinal bleed. But if it comes back negative, then it isn't proof that a bleed doesn't exist. For that you'd need a colonoscopy as well. And it still wouldn't be definitive proof everything was fine if the result was negative.

Between an endoscopy and a colonoscopy there are yards of intestine that can't be seen by either procedure. The only choice for actually seeing bleeding and its cause is having a capsule endoscopy done. I don't know how easy they are to get on the NHS. I tried to get one and was refused but I know some parts of the NHS will do it. I couldn't afford a private one. And sadly, even a capsule endoscopy isn't foolproof. They have a tendency to run out of battery power before they reach the end of the gut, and rarely last beyond the terminal ileum.


There is another possibility (non-invasive) to check for bleeding, and that is getting a faecal occult blood test done (of the kind used in bowel cancer screening) but getting the conditions right to avoid a false positive or a false negative can be difficult. Read the following post for more details :


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Thanks for this humanbean - very useful information. I am certainly considering doing the bowel screening test - I have had the kit for ages and keep putting it off given the not very pleasant nature of it. I notice that I would have to stop taking the iron tablets beforehand but as I had a blood test this week which included iron levels, I'll wait for the results of that before just stopping.

Given this information, it's slightly surprising that my GP didn't suggest doing the test - us over 50s in Scotland should be screened every two years, and you can get a 'shit kit'(!) on request. Although not the nicest thing in the world, in my case its preferable to an endoscopy!

The capsule endoscopy sounds intriguing, but I very much doubt whether it would be available on the NHS, although might be worth looking at as a future private option if all other avenues are inconclusive.

Thanks for your advice!

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