How safe it is to change the gender (transition from female to male) ?

female to male is safer than vise-versa 'cuz the doc doesn't have to create a vagina, uterus, cervix, etc; they only got build a long tube (penis) and attach it. Easier...

male to female is harder because there's a bunch of reconstruction going on

It's pretty safe if you do the research on the doctor before going through with it. If the doctor's reputation proves him/herself, then you should be alright. There are no guarantees you'll have a good reaction to the hormones or the post-surgery medicines and what not. The best way to stay safe is to know what the doctor is saying. Ask questions and know the doctor very very VERY well before going through with anything. The more you know the more you'll figure out if the doctors the right one for you.

It has different effects on everyone. But it is pretty safe. Taking T can make you aggressive and angry if you don't take the right doses. And of course there are risks with any surgery. But if you are informed and have good doctors you'll be fine.

Its safe - but a long, time consuming that is very costly - emotionally and financially. See the attached site for some peoples' experiences.

its safer than MTF for one reason:

trans men pass better, their face masculinizes faster and more completley so its harder to tell they are trans, so its much less chance of being killed

other than that im totally transissioned and i have had no real physical problems aside from my cholesterol going way up, otherwise im healthy

its a hard road and a difficult life being trans but its better for me than being in the body i was born with

one can change safely enough but being accepted is another issue all together!