Well, yes, urine contains toxic elements in it which may cause harm if taken in high concentration.

If a person gets lost in a desert and unable to find water, he may drink his urine once but doing this over and over again may lead to his own death.

And yes one idea is that, one can collect his own sweat which is less toxic than urine and may drink it. But as said it is also saline and may speed up the dehydration.

By the way great article @curiosity. Following your articles from the beginning. I also write about science but am not good as you. But you doing great job. Keep it up. :)