Thyroid UK
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Blood tests - which are the necessary ones

Hi everyone

I have just recently been diagnosed with hypothyroidism having a blood test for something else and my tsh level came back at 65 so dr immediately put me on thyroxine 25mg/50mg. 6 weeks another blood test, tsh down to 38 so on 75mg but since I started on thyroxine I have started to feel all the symptoms, joint pain, exhaustion, fluid retention (weight gain), painful feet, leg aches and really struggling to finish my days at work. Luckily I spoke to thyroid uk who told me to request full thyroid tests - free t4, free t3 etc so next results gave more information and it looks like I have low vit d and vit b12 and also tpo antibodies. - the dr only said my vit d was a bit on the low side so I could take a supplement, nothing about vit b12 and tpo antibodies. So dr again upped thyroxine to 100 and said come back in 12 weeks.  I said no I would take it for 4 weeks and if no improvement I want to see a specialist.

so what I would like to know is what tests should I be asking for as I can see going forward I will probably have to get them done privately and regularly until I get myself sorted.  I didn't have reverse t4/3 on my last blood test is that necessary?

Also how long does it take to get levothyroxine into your system? As dr put me on 100mg and said comeback in 12 weeks - if I'm not right at moment surely 6 weeks would give good indication?

I am taking vit d 5000 & vit b12 2000 at the moment as I don't want to take anything for fluid retention or other symptoms n case I mask how I am really feeling before i find out what is going on with my body.

6 Replies

If your calcium is high due to vitamin D supplementation I think that can cause some of your symptoms. Don't take vit d without k2. I would just be cautious about taking it overall because it can cause problems too. I would ask for all the hashi/hypo tests: free t3/t4, conversion and a scan as well as tsh and also parathryoid testing, pth and some of the other vitamins too maybe. Good luck, I hope you feel better soon. 

I think it takes about 4-6 weeks for levothyroxine to build up in your system. My father had to stop his because he became hyper and had high bp and other symptoms. I have reduced my dose and will stop it eventually maybe. Unfortunately I keep getting migraines now when I forget to take it. I'm back to 25mcg now. My father who had much worse tsh and antibodies than me felt ill at 50mcg. 


Many thanks, it is so helpful having this site as the dr will only respond if you come up with the questions. 



Ideally TSH, FT4, FT3, thyroid peroxidase (TPOab) and thyroglobulin (TgAb) antibodies will be tested.  NHS primary care rarely tests FT3 unless TSH is <0.003, or TgAb, and NHS doesn't test rT3. 

If TPOab are over range it means you have autoimmune thyroid disease (Hashimoto's) which causes 90% of hypothyroidism.  100% gluten-free diet may improve symptoms and reduce antibodies.

It takes 7-10 days for a Levothyroxine dose increase to be absorbed  before it starts working and in the meantime your hypothyroid symptoms may have been getting worse.  You should start feeling some improvement now but it will take up to six weeks to feel the full impact of the dose.

You should have a follow up thyroid test 6-8 weeks after a dose adjustment.  Arrange an early morning and fasting (water only) blood draw when TSH is highest, and take Levothyroxine after your blood draw.

Most people will find symptoms resolve after their TSH drops to around 1.0 with FT4 in the upper range but symptoms can lag a couple of months behind good biochemistry.

For maximum absorption Levothyroxine should be taken with water 1 hour before or 2 hours after food and drink, 2 hours away from other medication and supplements, and 4 hours away from calcium, iron, vitamin D supplements and oestrogen.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Many thanks for that.

I do take my thyroxine first thing 5.30 and don't have anything apart from water until breakfast at 10 but I did take my vit d & vit b12 with it - I will now take those at night.



Fat aids absorption of vitD which is why it should be taken with the fattiest meal of the day.  You can take your B12 at the same time.


Ok will try and have with my dinner, thanks.


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