How long ago were these vitamin tests done? Do you have the ranges.
If several months ago you need to recheck levels of vitamin d, b12, folate and ferratin. These all need to at good (not just average) levels for thyroid hormones (our own or replacement ones) to work in our cells.
Also have you had thyroid antibodies checked? There are two sorts TPO Ab and TG Ab. (Thyroid peroxidase and thyroglobulin) Both need checking, if either, or both are high this means autoimmune thyroid - called Hashimoto's, the most common cause of being hypo. NHS rarely checks TPO and almost never checks TG.
If you have Hashimoto's then you may find adopting 100% gluten free diet can help reduce symptoms, and lower antibodies too.
If you can not get GP to do these tests, then like many of us, you can get them done privately
Blue Horizon - Thyroid plus eleven tests all these.
This is an easy to do fingerprick test you do at home, post back and they email results to you couple of days later.
Usual advice on this test, (home one or on NHS) is to do early in morning, ideally before 9am. No food or drink beforehand (other than water) don't take Levo in 24 hours before (take straight after). This way your tests are always consistent, and it will show highest TSH, and as this is mainly all the medics decide dose on, best idea is to keep result as high as possible.
Assume you know that Levo generally should be taken on empty stomach and no food or drink for at least hour after. Many take on waking, some prefer bedtime, either as more convenient or perhaps more effective. No other medications at same time, especially iron or magnesium, these must be at least 4 hours away
Best advice is to read as much as you can. Vitamin and minerals levels are very important, but standard NHS thinking, doesn't at the moment seem to recognise this. You will see, time and time again on here lots of information and advice about importance of good levels of B12, folate, ferritin and vitamin D - not just at bottom of range ......
Also gluten connection to autoimmune Hashimoto's, if you have high antibodies, and not gone gluten free already then you may find this helps reduce symptoms and lower antibodies