Although your GP could trial you on Levothyroxine for 3 months to see whether symptoms improve most GPs won't diagnose hypothyroidism until TSH is over range. TSH 4.0 is usually high in range, but not over range. FT4 and FT3 results above are good.
Auto-immune Thyroiditis - or Hashimotos is the most common Thyroid illness throughout the world - so without testing how would they know ? When I was diagnosed with HIGH anti-bodies/Hashimotos - the TSH - FT4 and FT3 were all within range - so obviously not normal for me !!
Many people have clinical symptoms but remain undiagnosed. This is from Thyroiduk.org.uk and may be helpful. You should ask for antibodies to be test as that would mean you have an Autoimmune Thyroid Disease if you have them:-
When you have a blood test it should be the earliest possible and fasting although you can drink water. Also don't take thyroid hormones until after the blood test as it can skew results.
Ask for B12, Vit D, iron, ferritin and folate to be tested as well as some of the ones on the above link.
Also, always get a print-out of the results with the ranges as labs differ and it makes it easier to comment.
(( am not medically qualified but am hypothyroid - and remained undiagnosed for a long time as no-one took the necessary blood test)
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