Hi,
I've been on thyroxine since I was 21, now in my 40s.
If you've only been on it a year it's very possible that your levels need testing and you may need an adjustment. Thyroids can deteriorate slowly. Remember you can adjust slightly by a 25 tablet on alternate days if needed - always through Gp. Ask Gp to help you maximise your dose to around tsh 1 or a bit lower and see how you feel after a few months.
They key thing with taking it is consistency. Taking at night on an empty stomach was found to produce better levels but this was due to timing with food and routine. I always forget so I have to do morning but with kids and chaos and needing to eat as soon as I can I do generally have it near my cup of tea or with
BUT I'm very euthyroid right now on a stable dose, tsh about 0.3. In practise, it's having a regular routine over at least 6 weeks.
Caffeine, milk, lots of fibre, calcium and iron tablets, indigestion medicine can interfere with absorption - you do really need to be more mindful of the medications and vitamins. In fact, taking regular beta blockers had more of an impact for me and I had to take 12.5 extra.
You can take with orange juice or ribena.
If you're going to make any changes to your routine, do so for around 4 weeks before getting any tests, but just make sure it's sustainable.
How much are you on? What was last blood test result? Always keep a record of these and nite how you feel. Get your tests done at the same time of day, morning is best, and take your thyroxine after the test as it can peak in the blood a few hours after taking.
Low Vit d, iron (ferritin), b12 can cause similar symptoms so it's worth keeping an eye on these. Iron and vit d can sometimes also be low if you've been hypothyroid, the iron due to how thyroid hormones affect iron metabolism. You need selenium, iron and iodine to help metabolise the t4 to t3. (Iodine is less important if you're on thyroxine but still good to make sure you're getting it.) t3 is the hormone your body actually uses for energy. T4 (thyroxine) is a pro hormone.
I've gleaned all this over the years from the British thyroid foundation, experience and a relative who researches in the area.