@Sparechange
Sometimes an under active thyroid is due to an autoimmune condition called Hashimotos
This is when your own immune system starts attacking your thyroid which means it can’t function properly and therefore becomes under active
This is what I’ve got, and unfortunately it does mean I get good and bad periods, because my thyroid function fluctuates
The medication dose that is good one month when my thyroid functions is then too low when it isn’t functioning, and therefore I feel a bit shit for a few weeks until I work out what is going on, then get a blood test, then get a medication review, then get my dosage altered
So you should ask your doctor if they’ve done an antibody test to establish if you have Hashimotos and if you have, tune in to your body
The things that have helped me stablise my Hashimotos:
Going strictly gluten free
Taking supplements (Holland and Barrett do a specific ‘thyroid support’ one) including a high dose of vitamin d - 6,000 a day leaves me in the mid-point of the range. Any less than that I am quickly become deficient
I have Hashimoto's too. It will be 2 years in April since I first had my private blood test that confirmed it (GP was useless). Like you, I also went fully gluten free last April (my husband did too to support me, and it has cleared up his acid reflux which is a bonus!).
I was put on a starter dose of 25mcg levothyroxine, it did nothing. In that time I've worked up to 150mcg, GP won't up it any more as TSH has gone under range and they are obsessed with TSH without taking anything else into account. I've now started adding some T3 medication which I bought on holiday in Greece in 2019 just in case, as it is practically impossible to get here because the NHS won't prescribe it because of cost.
I've gone from feeling utterly horrendous to just feeling unwell. There is no way I would have been able to hold down a job during this time, luckily I'm already medically retired thanks to a totally unrelated issue which is a good job.
Posters on here are right in saying that generally, when the right level of medication is reached then people will feel ok. However, that doesn't happen in every case, like me, and as a country thyroid conditions are dealt with very badly, particularly if they are auto-immune.
Vitamins play a very important part as they can be linked to how well your thyroid converts T4 to T3 (T4 is a storage hormone, T3 is an active hormone which is essential for your thyroid to function properly). The ones to concentrate on are Vitamin D, Vitamin B12 and ferritin.
Thyroid UK has an excellent online community where there are some very knowledgeable people. I have learnt so much about how thyroids work, tests, medication, how poor GPs are etc etc, and about how to help myself.
I'm not typing this to scare the op, but more to make them aware that while you'll hopefully be ok as the majority of people are, it's well worth learning what you can and being able to self-advocate, particularly with GPs. One of the most important things to do is get a copy of your results every time, which you are perfectly entitled to do. GPS are generally happy if you're "in range", however these figures whilst maybe suiting the majority don't suit everyone.