How do you get urine stains out of underwear?

If the incontinence is mild such as dribble when sneezing, coughing, laughing etc., try those incontinence pads in the bottom of underwear. If incontinence is worse, try the pull types of adult briefs.

Soaking those underwear overnight in a detergent will help as well.

Bleach pen but only on cottons.

My cure for #2 is cold water and baking soda, so perhaps it would help #1 as well.
Just toss them if it gets too frustrating!

Sometimes shampoo on the stains helps, but only if they are fresh. I keep a bottle from the $ store near the washer.

Oxi-clean takes too long to whiten. Bleach if cotton but can't be used on synthetics. I use Purex powder and it seems to help. I turn the underwear inside out and wash. Not sure how it would be as a soak and then wash.

As said, if this is a man, and its more than a trickle, he needs Depends.

You can try bleach, or Oxi-Clean but perhaps it's time for Depends instead. That way you don't have to worry about getting urine out of underwear and you just get to throw them away.