Biotrexate 50mg Injection is given under the supervision of a healthcare professional and should not be self-administered. Your doctor will decide what dose is necessary and how often you need to take it. This will depend on what you are being treated for and may change from time to time. You should take it exactly as your doctor has advised. Taking it in the wrong way or taking too much can cause very serious side effects. It may take several weeks or months for you to see or feel the benefits but do not stop taking it unless your doctor tells you to. You should avoid drinking alcohol as it may increase your risk of liver damage.