Is there any way to quickly lower cortisol?

First confirm whether your cortisol is actually elevated before considering supplements—don't take them long-term on your own.

I'm skeptical about ashwagandha. It works slowly—usually it takes several weeks of consistent use before you notice any effect—and it may not be suitable for people with thyroid issues. Magnesium and phosphatidylserine are relatively gentle, but expecting to fix both sleep and weight within a few days isn't realistic. Supplements are only supportive; without addressing your daily routine and sources of stress, it's hard to see noticeable changes.

One more boundary to keep in mind: high-concentration ashwagandha may affect blood sugar and blood pressure, so anyone taking blood pressure or blood sugar medication shouldn't casually add it on top. Also, cortisol itself follows a circadian rhythm, so a single high reading at one point in time can easily lead to a misjudgment.