It depends on your state's laws, but generally people who are voluntarily committed are still permitted to obtain firearms -- some states require a 2 year record of good mental health. Some may be stricter, I'm not sure. Certain states do not perform any sort of background checks at all, so it really just depends.
But what you are doing right now is really dangerous & I think you need to choose living & getting healthy over firearms, if it comes down to it. Not getting help b/c you are worried you won't be able to purchase a gun in the future is really not a bright idea.
I'm not sure what you mean by "I have a permit". Are you talking about a driver's permit? If so, the hospital will almost certainly report to your parents since you will need to list a legal guardian to make decisions for you while you are on the ward. They also almost never release a person who was self-injuring on their own; usually a family member would need to come to pick you up & sign the release instructions saying that they will keep an eye on you & call the hospital if you start to hurt yourself again. Beyond that, it is incredibly expensive to stay in a psychiatric hospital/ward, so if you can submit it through your parents' insurance that's a good idea.
You can typically bring anything that cannot be used as a weapon. That is, no shoelaces, no chains, no drawstrings in pants, nothing sharp, nothing with cords (blowdryers or such), no over-the-counter meds & nothing in which something dangerous could be hidden (pillows, stuffed animals or such). Prescription meds may or may not be taken from you. Certain meds can be prescribed by the staff doctors. Pain meds are generally not permitted.
You can bring journals as long as they are not those wire spiral notebooks, paper, books, or crafts. Some places will allow you to bring cards as long as you're willing to play for fun & not to gamble. Some hospitals will allow cigarette smoking at certain times of the day, others do not allow smoking at all.
Know that ALL of your possessions, including the clothes you come in with, will be searched thoroughly & any items deemed to be dangerous or not conducive to healing (games, cell phones, etc.) will be taken from you & put in storage. You should not take more than $20 cash. Do not take more than one credit card. Bring your insurance card & a photo ID. Bring a paper list with local numbers of family & friends (usually you will be permitted to make at least one phone call per day to a local phone number -- sometimes they limit it to family, but usually calling friends is permitted as long as they are not deemed a negative influence).
Bring all your toiletry items -- soap, shampoo, toothbrush, toothpaste, comb/brush, etc. Do not bring dental floss or mouthwash as those items will be taken away. Keep things simple, as styling products & other "luxuries" are not permitted. Sometimes the nurses will keep your toiletries & supervise your use of them, other times they will let you keep some or all of those items in your room (it depends on the doctor's orders for what is to be considered a danger to you & what is a danger to your roommate). Usually they can get you the necessities if you forget something, but generally it is best if you can remember most items.
Do not pack your items in a really nice bag, or take anything that you would terribly miss if it were lost as that does happen far more often than it should. The nurses are focused on patient care & caring for belongings often falls to the wayside. Your bag will be taken away from you due to the straps & put in storage as soon as it is unpacked, so that is why I am suggesting it not be too nice.
Jamiee gave you good advice about going to the psychiatric triage unit. However, not all hospitals are large enough to have a psych triage (at least here in the U.S.) so if you are not going to a dedicated psychiatric hospital, you can just go to the ER at any medical hospital, tell them what is going on & the triage nurse will direct you what to do (not all hospitals have psych wards, so sometimes it means waiting until a mental health worker can be called in to evaluate you). If you can get a hold of your psychiatrist & get pre-admitted, that would be much better b/c you wouldn't have to wait or go through lengthy evaluations. BUT, the waiting is well worth it if you need immediate help b/c you can't get in touch with your psychiatrist & you are planning to take an overdose of ibuprofen. If you go to the ER, you can give them the name of your psychiatrist & that should help some with the waiting time.
Things really can get better. Making good decisions one at a time will get you there. I was so miserable every minute of every day 2 years ago. After a lot of help, I have gotten much, much better. I still have my bad days, but they are far fewer & not nearly as horrible & overwhelming as they used to be. But it took me laying everything else aside (what will people think of me, what if I can't serve in the military, how will this affect my ability to get a job, will colleges ask about this & refuse to let me in b/c I went to the hospital, etc.), to finally realize what the right decisions were. As it turned out, going in voluntarily meant that, in my state at least, I don't have to report it anywhere to anybody. That has been a huge relief, but honestly, looking back, even if it cost me those things, it would have been worth it b/c I would still be alive.
I hope you make the best choice for your health & your life. Let us know how we can support you & keep taking care of yourself.
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