For your Vit D, again your GP has been negligent if he started you on 800iu D3 five years ago, you would most likely have been less than 30nmol/L at that time which means you should have been given loading doses.
So just take charge here and buy your own D3 and take 10,000iu daily for 4 weeks which gives 280,000iu which is the loading dose (280,000 - 300,000iu is the amount given for loading doses. Then reduce to 5000iu daily. Then retest 3 months after starting, you can do this with a home fingerprick blood spot test from City Assays vitamindtest.org.uk/index.html
When you've reached the level recommended by the Vit D Council, which is 100-150nmol/L, then you'll need to find your maintenance dose which may be 2000iu, may be more or less, it's trial and error so we need to test once or twice a year to keep within the recommended level.
When taking D3 there are important cofactors needed vitamindcouncil.org/about-v... D3 aids absorption of calcium from food and K2-MK7 directs the calcium to bones and teeth where it is needed and away from arteries and soft tissues where it can cause problems. D3 and K2 are fat soluble so should be taken with the fattiest meal of the day, D3 four hours away from thyroid meds.
Magnesium helps D3 to work and comes in different forms, check to see which would suit you best and as it's calming it's best taken in the evening, four hours away from thyroid meds naturalnews.com/046401_magn...
Check out the other cofactors too.
For the iron deficiency anaemia (confirmed by low MCV/high MCHC) here is the NICE Clinical Knowledge Summary for treatment cks.nice.org.uk/anaemia-iro...
Print off the relevant part and show your GP then ask for the appropriate treatment
"Treat adults with iron deficiency anaemia (including pregnant women):
Treat the underlying cause, if appropriate to do so in primary care.
Treat iron deficiency anaemia with ferrous sulphate first-line and advise about diet.
How should I treat iron deficiency anaemia?
Address underlying causes as necessary (for example treat menorrhagia or stop nonsteroidal anti-inflammatory drugs, if possible).
Treat with oral ferrous sulphate 200 mg tablets two or three times a day.
If ferrous sulphate is not tolerated, consider oral ferrous fumarate tablets or ferrous gluconate tablets.
Do not wait for investigations to be carried out before prescribing iron supplements.
If dietary deficiency of iron is thought to be a contributory cause of iron deficiency anaemia, advise the person to maintain an adequate balanced intake of iron-rich foods (for example dark green vegetables, iron-fortified bread, meat, apricots, prunes, and raisins) and consider referral to a dietitian.
Monitor the person to ensure that there is an adequate response to iron treatment."
If necessary ask for a referral to a haematologist.