Advice please for my Daughter

Dwsmith, yes treatment is Levothyroxine.

I don't see why your GP should be annoyed you've had private tests she wouldn't do. It saves her practice the cost of testing.

Your doctor sounds positively dangerous. Your daughter has or has had :

Severe iron deficiency

Low in range B12

Low in range thyroid hormones

And your doctor is doing practically nothing to fix this and then is leaving your daughter to rot. The poor girl must feel terrible!

I know from personal experience that severe iron deficiency can lower thyroid hormone output. Until you get iron up to a healthy level you won't know whether this will be sufficient to perk up her thyroid or not. Thyroid treatment may still be necessary, but I would hold off just a little bit until you get her nutritional levels at a sensible level. It might be enough, it might not be.

Ferritin needs to be mid-range. Just getting the level into the bottom of the range is not good enough. As you say, unless the conditions that made her so anaemic in the first place aren't fixed or understood the likelihood is she will just drop low in range or under range again.

Very low B12 needs to be followed up urgently - low B12 causes neurological damage which will become permanent if left for too long. But first, your daughter needs to be tested for pernicious anaemia. Until she has those tests she should NOT supplement B12 or B Complex because it makes the testing unreliable. As soon as B12 is supplemented it is very hard to get a diagnosis of pernicious anaemia at all. If the tests come back negative then supplement with either Jarrow Formulas or Solgar 5000mcg methylcobalamin. High in range or over the range B12 is not dangerous (unlike other nutrients for which more care is needed) if it is caused by supplementing. Also, supplement with a methylated B vitamin complex to go with it. The only one I know of is Thorne Research Basic B Complex, take one a day.

Another personal anecdote, but one which is common to many of the people who come here - I tested negative for coeliac, but when I gave up gluten as an experiment all sorts of things improved for me. My ferritin levels rose quite dramatically for a start. I'd spent nearly two years taking iron supplements and my progress was achingly slow, and if I stopped taking iron my levels dropped rapidly. Giving up gluten was the thing that made the difference. I suggest your daughter tries this. It has to be done 100%, it isn't possible to be "almost" gluten free, you simply can't cheat.

It is clear to me that to me that your daughter needs a new doctor as soon as possible. The one she has been seeing will not make her well. If you see another doctor and still get no joy with the iron levels, then your daughter will need to supplement. But I'm reluctant to suggest iron supplements for someone who is legally still classed as a child. Unlike B12, iron supplements can be dangerous in high dose or overdose, and although it is unlikely that overdose would occur quickly in someone with very low levels of iron, I still feel it is something a GP should monitor.

I should also have said above...

Vitamin C supplements are a good idea and don't need to be monitored. Decent quantities of vitamin C help the body to absorb iron and so should be taken with supplements (if your daughter ever gets to take some!), or with food. Get supplements which are 1000mg or 1g, and take one per meal or per iron supplement. Start with just 1 per day with a main meal, after a few days add a second with a different meal, then a few days later add a third with meal 3. The only side effect to watch out for is diarrhoea. If that happens reduce by one pill/capsule.