How long does it take prednisone to get out of your system?

It takes approximately 16.5 to 22 hours for Prednisone to be out of your system.
The elimination half life of prednisone is around 3 to 4 hours. This is the time it takes for your body to reduce the plasma levels by half.
It usually takes around 5.5 x half-life for a drug to be completely eliminated from your system.
This is (5.5 x 3) 16.5 hours to (5.5 x 4) 22 hours for Prednisone.

Other factors also need to be taken into account and include:
1. How much and how often you have taken the drug.
2. Your metabolic rate – a slower metabolism will increase the time a drug remains in your system.
3. Your age and health – older age and poor health will generally increase the time the drug stays in your system.
4. Body mass – generally the bigger you are the longer a drug will remain in your system.

See also: https://www.drugs.com/ppa/prednisone.html