Not dangerous per se, as mentioned above.
But anything over 3 indicates either low thyroid or your pituitary is playing jokes on you.
I was exhausted at 3.4 TSH. do you have any symptoms??
It's not 'dangerous'. It won't kill you ,but it might make you feel pretty lousy.
The other thing to remember is that the TSH is not from the thyroid but the pituitary gland.
You need to be looking at your Free T4 and Free T3 as well, as if they are off you would need treatment.
Do you have any symptoms? Lots of people have high TSH and have no symptoms yet others feel lousy.