Lizbet8 So there we have it, official proof that your doctor is a complete and utter twonk (and I'm being oh so polite) so let's add him to the Cr@p Doctor Pile.
Ferritin at 15 is absolutely dire. I would ask about iron injections, you might have been offered them if your level had come back at 14 (but no 100% sure of that). Ferritin must be half way through range. Thyroid hormone can't work if it's less than 70, but your doctor won't know that. If you're not allowed iron injections you need some very serious iron supplements, take each tablet with 1000mg Vit C to aid absorption and help prevent constipation. Take iron 4 hours away from thyroid meds and other supplements as it will affect absorption.
B12 is to low. Anything under 500 and there's a risk of neurological problems. The Pernicious Anaemia Society recommends 1000. Take Solgar or Jarrows sublingual methylcobalamin lozenges 5000mcg daily for 2-3 months then reduce to 100mcg daily as a maintenance dose.
When taking B12 we need a B Complex to balance the B vits. Thorne Basic B or Jarrows B Right both contain 400mcg methylfolate which will help increase your poor folate level. That needs to be at least half way through it's range. Take B vits in the morning, no later than lunchtime as it can be stimulating and you don't want it affecting your sleep.
Vit D, as it says, is sub optimal so your doctor should have addressed this. You need to get that up to 100-150. Take D3 5000iu daily for 3 months then retest. If GP won't do it get a private blood spot test done with City Assays for £28. Once between 100-150 reduce dose to 5000iu alternate days.
When taking D3 we also need the co-factors K2-MK7 and magnesium. Vit D aids absorption of calcium from food, K2 directs the calcium to bones and teeth rather than arteries and soft tissues. Vit D and K are fat soluble and should be taken with dietary fat.