Thyroid UK
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Testing Ferritin Levels

Long story short: About a year ago my ferritin levels were on the floor (4ng/ml, range 15-200ng/ml, I think, not sure), was prescribed ferrous fumarate and the level climbed over the course of about six months to 70ng/ml or so. Since it was at a good level my GP and I agreed that I should drop down to one ff capsule every other day.

It's now time to retest. Which would yield the most useful and / or interesting result: taking the ff right up to the day of the blood test, or stopping a few days beforehand? I can't see my GP going for two tests in a short space of time so can't do both :) If I were to stop taking the ff a few days before, how many days should I leave between stopping and the blood test?

I realise, now, looking at the range and the last test result, that cutting back probably wasn't warranted at the time and that I was only just where I needed to be (it looked like I was close to the top of the reference range but now I really can't trust my eyes). I'm losing quite a lot of my hair and I hadn't twigged that it might be that my ferritin was too low again (although probably in range). Still, I'd be interested to know which method would give the most interesting result.



8 Replies

Hose, stop supplementing iron 7-10 days prior to the blood test.


I thought I'd read that somewhere so it's good to have it clarified. Is that because it will give a good indication of what my natural levels are?


Hose, no, I think its more of a guide to how well you're holding on to the iron. If you want a baseline result you'd have to stop supplementing for 4 months prior to testing to allow red blood cells turn over and renew.


I might see if I can get my GP to agree to that, but that might mean feeling suckily awful for four months. On second thoughts, maybe not!


This might also explain the conversion problem I'm having... Although it could be poor adrenal function or genetic or... Frankly, the list just goes on and on. Sometimes I start to feel like a dog chasing its own tail :-/


As well as stopping the iron for several days as Clutter mentioned above, make sure you get tested first thing in the morning, having not eaten or drunk anything except water for 12 hours before the blood draw.


I wasn't aware that the ferritin test was a fasting one.


It mentions it on this page :

The link does refer to iron blood tests, rather than ferritin blood tests, so fasting for ferritin may be unnecessarily cautious. The choice is obviously yours.

As a personal choice I arrange all my blood tests for as early as possible in the morning, and I always fast except for water. If I always stick to the same conditions for every test I feel it maximises my ability to compare like with like.


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