Hi have a question

I have my old bass back from when i was a teenager. No idea what i did to it. The action to INCREDIBLY high. (Distance between stings and frets) sorry i'm not too good at terminology.

Is there anyway this can be fixed? Its not a dual action truss if this matters.

It depends on why the action is so high. If your bass has been sitting unattended for years, the neck may be bowed. If so, you need a truss rod adjustment. In most cases, a 1/4 to 1/2 turn is all that is needed to correct the problem. But it could be something else. I take it the bass did not always have this unusually high action?
"Maybe this world is another planet's hell?" - Aldous Huxley
I can't remember what a teenage me did. I was into messing around it's been stringed for at least 8 years. Does righting the rod move the centre on the neck towards the strings? When I say it's high it's almost 1cm on the 12 fret.
Yes, weather conditions and other factors can affect an unused stringed instrument's neck in the way you describe. A truss rod adjustment can indeed fix it quickly. You'll need to get rid of those old strings, though. After that many years of not tuning it, they could break when you attempt to tune up the strings. You don't want to be holding an electric bass when a string breaks. They can be almost lethal when they go flying.
"Maybe this world is another planet's hell?" - Aldous Huxley
Go EASY on the truss rod adjustments! Try a 1/4 turn and see if it fixes the problem. That's 1/4 of a full 360 degrees; not 1/4-inch! Most truss rod adjustments don't need more than a 1/2 to 3/4 turn. Occasionally, some do, and I suggest taking those in to a repair shop to have them do it. They can tell if there is something else going on.

You might need to LOOSEN the truss rod. Go to YouTube and check out a few videos or just Google it and see which one is best for you. There are plenty of good demos on the subject.

Also, use the right size socket wrench - unless your truss rod adjustment device is a wheel. And if you play a Rickenbacker with its double truss rods (some Trabens have them, too), then take it to a good repair tech. Synchronizing those two truss rods is a royal pain in the ass. Leave it to a pro.

Good luck! It's probably an easy fix.
"Maybe this world is another planet's hell?" - Aldous Huxley
Glad to hear it! Enjoy that bass and keep playing!
"Maybe this world is another planet's hell?" - Aldous Huxley