I have been dying my naturally dark brown hair for over a year and a half.

In September I dyed it a permanent medium brown colour, then in the first week of December I dyed it a supposedly semi-permenant dark brown, almost black.

I have recently tried to dye my hair back to blonde but the colour only went up one shade but at the roots went very light.

Do I need to get my hair stripped and then dyed blonde? Or can I just buy a very strong blonde and dye it again, if so, when should I do this?What should I do?

"Color won't lighten color" is a mantra in the industry. Yes, you should have used a color remover to remove the dark artificial pigments.

The question I have is, "did you try to use bleach to go blonde or did you just use a blonde haircoloring?" If you used bleach, you've probably over-oxidized the artificial pigment and you're out of luck. If you used a single-step blonde haircoloring, you can remove the color and re-dye. You will probably need more than one application of color remover to get all of the dark out.

Use ColorFix, Color Zap, Color Oops, or Igora Phantom for stripping. Do not use Effasol or bleach.

Instructions for using ColorFix:

Hair Color and Hair Care by Robert Craig Salon Products, Ltd.

I didn't use bleach just a packet hair dye, but I'm guessing most of these blonde dyes have bleach in them?

No, actually most blonde dyes do not have bleach in them. They use peroxide for lightening and if you look at the side or back of the package (if you buy a packaged dye), they will show you the shade to expect if your hair is such and such a shade. Typically, they won't lighten more than two shades without a lot of brassiness.

ColorFix first is your best bet. That will strip the artificial pigment from the hair. It will most likely leave your hair an artificial red, orange, or yellow color. That's to be expected so don't panic. After that, you can use another dye.

If you really want to go blonde, I suggest you go to:

Bottle Blondes Board

Or

The Going Blonde Message Board

And post some questions there.