MDxx made with the "Aluminum Amalgam" method can have very toxic Mercury compounds in it. MDxx made with other methods, most likely will not contain them.
Don't take it if you are 14, but if you choose to ignore this advice, then:
If this is your first time then do not take more than 80mg, because you do not know if you are not one of the few people that are exceptionally allergic/sensitive to it. The second time around you WILL know whether you are exceptionally sensitive.
Even if nothing happens to your friends, you can become very sick with the same dose.
To calculate the effective dose, you need to know your weight, because skinny people need a smaller dose than fat people.
Besides the dose, you can help your body to deal with the MDxx better by following
this thread.
You should get a test-kit to test that you really have MDxx or send a sample to a professional lab that can detect its organic composition and presence of Mercury. You might be surprised that the MDA powder is an MDEA powder or just MDMA, or not MDxx at all.
I have to warn you that there is a lot of bad European MDxx powder out there, that can cheat the simple tests.
You will know that the MDxx is bad if the pupils of your eyes do not dilate like in
this picture.
If you encounter such bad MDxx, report it in
this thread.
If you get high anyway, stay away from hot places because high temperature + MDxx can damage your brain.
If you are thirsty do not drink a lot of pure water because that can lead to hyponatremia, which can kill you. Instead, drink isotonic sports drinks like Gatorade or water with sugar, lemon juice and two pinches of kitchen salt. The salt is very important !
If you want to keep your brain safe, let it recover for at least 3 months before another dose of MDxx.
P.S.
MDA lasts longer and is more physically stimulating and trippy while MDMA is more empathogenic at the same dose, so don't expect to be spontaneously talking to someone you don’t usually talk to or to be chatting for hours to a dude and thinking he’s your best mate.