My 5s battery is weird.

[nikabobriht]

It drops from 20% directly to 8%, and 5% soon, and dead.
I've run a test through my battery and it shows that the battery is only 10% worn.
What should I do??

 

[T5BRICK]

Replace the battery.

Turn off the percentage indicator.

Enjoy your phone. Plug it in when you can and run it from the battery when you need to.

 

[BearBert]

What you're describing is usually a good indicator the battery needs to be replaced. You said you ran a test and it said 10% wear, but what was the charge cycles?