A few months after my first concussion I did some bloodwork and it was found that I had a very low b12 (level of 133). I was very weak and exhausted with high levels of anxiety, I started to slowly improve until I got my second concussion.

I supplemented with 2000mcg (per doctors orders) for a few months, got my blood rechecked and my level was >1500. I then cut down to 1000mcg a day and my level was 485.

I have been on the 1000mcg dose for a while now, but am wondering if I need more? I use Bulletproof supplements with success and they have a b12 supplement that is 5000mcg, is that too high or could it benefit me?

There is the general RDA amount that drs/blood tests cover..
There is also higher therapeutic dosages for possible added health/healing..

Vitamin B12 - Consumer
NT has B12 topics in many other forums here- a site search will find those.

You might also consider trying a MSM supplement, or Grape seed extract..
benefits of MSM - Google Search
grape seed extract benefits - Google Search

The RDA is very low, 3 mcgs or so. Many of us take 1000 mcgs a day. B12 is not absorbed well in the gut. Depending on the dose available at a good price, sometimes I take a 2000 mcg lozenge each day. I usually get the Now brand at VitaCost because it is a good price. I prefer to get the methylcobalamin version, not the cyanocobalamin version.

The healthy blood level of B12 is 370 pm/mL to 960. I keep my levels at the top of the range taking 1000 to 2000 mcgs a day.

Blood levels do not indicate utilization.