Once you do start shooting your drugs, there is really no going back. I don't think if you ran out of needles you'd just smoke or snort it, you would most likely reuse an old needle. I know you don't think that will happen, that you will just go buy more; but I can't count how many times I've woken up dope sick in the morning, and the pharmacy isn't open... or I just don't want to walk there. Since I started IVing, heroin, that's the only way I will take anything. It definitely becomes a fixation in and of itself. During a period of sobriety I used to just shoot up water when I was having cravings, because you attach that feeling to that object.
By the way...I'm 25 years old. Two years ago, I shot up (have been doing so since I was 18), and woke up in the hospital 7 days later on a ventilator. Apparently I had passed out on the porch of my 3rd floor apartment, and no one found me for 3 days before I was even taken to the hospital. I had had a takotsubo cardiomyopathy, where my left ventricle bloated due to the adrenaline/stress, but the inability to react to it. I developed a blood clot in my left ventricle, had several minor strokes, and bed sores (from being in the same position for too long). I was unable to walk for 9 months because of the strokes and the awkward position I passed out in, and am lucky to be alive.
To this day, I have a noticeable limp, even though I've been in physical therapy since the accident; I cant feel the last two digits on my left hand; my pupils are two different sizes, as my right one won't constrict; and my right leg constantly feels like it's on fire, due to the nerve damage. Guess what, I took up shooting up again a couple months later. It changes the way you prioritize things... in a way you can't imagine unless you've done it.
That said, if you are going to do it, I would echo what everyone else has said: Micron filter, sterile water, new needle (though I prefer 29g long tips because you KNOW when you've hit a vein and solidly anchored in one), go parallel to the vein not straight into it, use a tourniquet above your bicep (and don't leave it on for too long). If you have trouble, a hot compress and proper hydration helps. If you aren't positive you're in a vein, stop shooting immediately and take the tourniquet off to try again later. It's easy to blow veins by fishing around or going straight through and leaving it on.
Good luck. I hope you really think hard about this and actually write out a pros/cons list. Think about the people you would leave behind if you died. Think of potential freak accidents like mine. Above all else: just be careful.
