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Pernicious Anaemia Society
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folate and ferritin test

I'm scheduled for a RBC folate and a ferritin test tomorrow.

1. Which is the better folate test, serum or RBC?

I've only been tested twice for folate, Nov 2014 and Feb 2015. It was a serum folate test and both times was high, >24.0 (range 3.0 - 17.0). So my doctor thought my folate was fine. Could it have been fine in serum but low in the cells? I convinced my doctor to test the cells as I am doing rather poorly lately. Have never been told to supplement folate (nor anything else for that matter) so I haven't. When I get a B12 injection I feel terrible for a couple of days, could it be folate I need?

2. I'm also getting a ferritin test. My HMO doctor has only tested it once, in Nov 1014, it was 113 (range 22 - 391 ng/mL). Shouldn't ferritin be regularly monitored? My PA treatment regimen began in Nov 2014.

I have had ferritin tested by a naturopathic doctor on the side as I felt I was getting dreadful treatment by my HMO. Ferritin has decreased over time and in June it was 61 (range 10 - 232 ng/mL). Do I need to supplement?

I did finally convince my doctor to order a ferritin test as well, since it hasn't been tested in so long.

2 Replies


Sorry but I'm not sure about which folate test is better. I've assumed you're in the UK.

It might be helpful to look up "MTHFR mutations". Some people have a genetic mutation that means their bodies do not metabolise folate as efficiently. I think some with MTHFR mutations find that methyl folate is a better option than folic acid. I use methyl folate as I think I may have a problem with the methylation cycle.

It's probably unlikely that you'll get MTHFR mutations checked for on the NHS but it is possible to have private tests for them in the UK.


Your ferritin is fine whether its 113 or 61 as it is neither too high nor too low. People often interpret this test wrong, and there is a school of thought that says you need it to be over 75, which I disagree with.

Ferritin is related to iron stores, but iron stores are not the only thing that affect it. It is also an acute phase reactant, meaning that it will elevate when there is inflammation. The difference between the two results could be related to that. Being very low on B12 could have caused your body to do strange things, that are now resolving (although I don't know how long it's been since you started to have B12 injections).

It's worth monitoring your iron levels to see if they continue to fall or will stabilise now, but don't rush into supplementing with iron "just in case". Inorganic iron supplements have all kinds of negative effects, from reducing absorption of other important minerals like copper and zinc, to changing the composition of your gut flora (everyone knows that iron supplements can cause constipation). They aren't a good idea unless you have a genuine iron deficiency.

Folate could be building up in your blood because you haven't got the other nutrients you need to metabolise it. One of those will be B12, but I believe other nutrients are required too. If that's the case, then taking more folate won't necessarily help, it will just pool in your blood too. You will need to think laterally to find out what other nutrients might be required (I don't think the NHS will take things that far). Some are mentioned here:



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