Regarding the timing of iron blood tests :
Source : nhs.uk/chq/Pages/1018.aspx?...
Iron blood test
Iron blood tests are usually taken in the morning before you eat anything. You should also avoid taking iron pills or tablets for 24 hours before your test. Your body absorbs iron very quickly from food or pills, so this can raise your iron levels and affect the test results.
Source : stopthethyroidmadness.com/l...
NOTE: for most of the below, we learned from our more progressive doctors that you’ll need to be off what you are testing for a minimum of 12 hours, i.e. take nothing the morning of the test. For iron, we learned to be off for 5 days based on information from the Iron Institute, i.e. to see what we are “holding onto”.
Regarding gluten :
I was tested for coeliac disease and it came back negative. Last year, several years after the negative results, I went 100% gluten-free, no cheating (although I did make some mistakes). I had struggled for nearly two years to get my ferritin up to mid-range and it increased agonisingly slowly, despite me taking 3 x 210mg ferrous fumarate every day. Within about 3 or 4 months of giving up gluten my ferritin shot up suddenly and quite dramatically to well over mid-range. I don't need to supplement any more and I don't get breathless. Could you try going strictly gluten-free for at least three months to see if it helps? You can always go back to gluten if it doesn't.
Regarding the supplements you take :
I've seen lots of people saying good things about ferrous (or iron) bisglycinate. (I've never tried it myself.) It might be worth a trial? It has more iron in than spatone.
There are other kinds of iron supplement. It is possible to take ferritin directly and also haem/heme. Helvella wrote about them here :
Since you have so many problems with iron you might do better with ferritin and/or haem/heme supplements. I think it would be worth the experiment.