How can I clean/fix black spots caused by dog urine?

Where? Hardwood? Carpet?

On hardwood floors or something else?

On hardwood floors I would use wood bleach.

The finish will have to be sanded away there and the bleach put only on the spots.

Hi Jessie. I'm Cindy. You could mix one-quarter cup of Hydrogen Peroxide, one-half cup of Baking Soda, and one teaspoon of Dawn dish soap. If your stain is on carpet, blot this on with a clean cloth, don't rub as that would push the stain further into the carpet fibers. Best wishes headed your way.

You can use hydrogen peroxide to lighten the spots. Put it on and set a damp cloth over it. repeat as needed.

How can I fix black spots on my concrete floor from the dog urine?

A mixture of one teaspoon Dawn dish soap, one-half cup baking soda, and one quarter cup hydrogen peroxide could be used. When staining carpet, use a clean cloth to blot the area rather than rubbing, since this will cause the stain to seep deeper into the fibers of the carpet.

Hi Jessie, hope this helps you. Hydrogen peroxide is one of the best chemicals to rid hardwood floors of urine stains. It is safe to use, and will not damage them either. Hydrogen peroxide is known for its effectiveness against dark and black urine stains. Apply it to a clean cloth and lay it over the stain, allowing it to sit and work on lifting the stain.