Why my iPhone battery health drains so fast?

Batteries degrade over time with usage, that's just how they work. You can expect about a 1% drop per month with average use on an iPhone.

Apple recommends replacing it when it reaches 80%

Here are some tips on maximizing battery life.

https://www.apple.com/batteries/maximizing-performance/

ishan103 wrote:

Why my battery drain so fast

https://discussions.apple.com/content/attachment/32e5a7f9-f947-4bf3-9312-11cafbd064f7

How long has it been since the phone was new?