Starting medicine with 5.4 TSH

Hello everyone,

I visited the doctor today since I’ve been experiencing mild to medium fatigue, muscle pain, etc for some time now with no apparent reason. I’m a male, 25.

My tsh came back with 5.4 value with my t3/t4 within range. I also had a vitamin b12 and vitamin d deficiency, my doctor told me that it’s not necessary to start medication right now but recommend 12.5 mcg medication and mentioned it’s a lifelong commitment, saying hypothyroidism starts with very vague indications e.g tsh could reduce and then show up at similar levels in a few weeks.

Should i start medication or just wait for it while taking vit B12 and D medication? How has been everyone’s experience? I cannot pinpoint why my thyroid isn’t working enough which makes me even more concerned as to what i did wrong, i exercise and try to eat good. I was told vit b12 is not being absorbed properly because of the thyroid issue.

Thank you for your opinions!