How long does methotrexate stay in your system?

It will take about about 2.3 days for Methotrexate to be totally out of your system.

The length of time it takes for a medicine to be removed from your body depends on the drug's elimination half- life. It takes 5.5 x elimination half-life for a medicine to be totally eliminated.
Methotrexate has an elimination half-life of 3 to 10 hours, therefore it will take approximately 55 hours (if we take the maximum time as 10 hours for the half life) which is about 2.3 days for it to be totally out of your system.

However other factors to consider 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.

For more information see:
https://www.drugs.com/pro/methotrexate-injection.html