The scenario is: You wake up, only to find you are bleeding from some random bodypart. You become hysterical. You've never menstrauted before! Why must you start now? Send it back! Send it back! You don't want to have to deal with moodswings and bloody underwear. You've always hated swallowing pills, and it embarrasses you enough just buying toilet paper. Well, RELAX. It might not be your period. Don't go crazy until you have to. It may be a simple mosquito bite, scratched open in the night. It coulld be a nosebleed, a cut, or an open gunshot wound.All of these are nothing to worry about. They have nothing to do with menstruation. Here is an easy-to-use guide, explaining the differences between menstruation and other types of blood.
 

Characteristics of a cut:

Characteristics of menstraution:

Can be anywhere on body. Hurts in that outsidey kind of way.  You can put a band-aid over it and feel all better.  You might get a really cool scar that you can make up stories about.  People will ask what happened.  You can whine about it and get out of doing a few household chores.  Nice clean blood flows out of it, clotting perfectly.  You can wash it out with peroxide.  Neosporin helps cuts heal four days faster. If you clot, you're not a hemophiliac.  Little kids get them and sing about them on TV, proudly brandishing their bloody elbows ("...I am stuck on band-aid brand cause band-aid's stuck on me..."). It means you were "playing to rough" (or maybe just chopping onions carelessly). When you go swimming, your band-aid comes off, and floats away to disgust other pool-goers.  You can peel off your band-aid and disgust/impress your friends.

Only leaks from genitals--female genitals, to be more specific. If the blood is oozing from any other part of the body, you can breath a sigh of relief. You are not menstruating.  Aching, intolerable, inside cramps.  You can jam a tampon over it and feel even shittier.  You might get toxic shock syndrome and vomit your guts out.  Dogs will be more likely to sniff your crotch.  You get moodswings and people will call you a bitch. Nasty old eggs flow out of you, staining the ass of your pants.  You must wash your panties in cold water, so as not to set the stain.  Birth control pills will regulate your periods.  If you get it, it means you're not pregnant.  Annoying women blab on about it on TV, descretely pouring blue liquid on pads.  It means you are "becoming a woman." You can't go swimming. You could peel down your underwear and scare the hell outta passersby/lose your friends/get arrested.