What Are The Side Effects Of Tyrax?

Good day! I have a life-timeTyrax 100mcg and 25mcg maintenance 30 mins. before breakfast, Sometimes drugstores do not have available tyrax and i asked if there is an alternative med. They advice me to take euthyrox (same Levothyroxine -Tyrax) Sometimes i fogot to take in 1 day is there an effect to my health? In taking the tyrax , what are the dos and donts . Thank you.