Medical questions & health advice by board certified doctors

"Why am I fainting?"

ZocdocAnswersWhy am I fainting?


Hi! Both last night and the night before, I fainted and blacked out for about 30 seconds. Both times were about 15 minutes after smoking weed. I know you're going to tell me it's from smoking, but I have been smoking for a couple years now and that has never happened before. It may have been caused by the Marijuana, but why is it just happening for the first time now? Are there other things that would cause it?


Thank you for this interesting question. In order to provide an accurate diagnosis, I would need to know the full details of your medical history and would also need to perform a thorough physical exam. In addition, you may need other testing. Only after collecting this information will it be possible to provide an accurate recommendation. Therefore, I strongly encourage you to schedule an appointment with a primary care physician. Fainting, or syncope, is a common medical problem with many potential causes. True syncope is defined as a loss of consciousness and postural tone that spontaneously resolves. It is certainly possible to lose consciousness or fall asleep after using marijuana, but it is atypical for this to cause true syncope. It is possible the marijuana was laced with another drug. Many people experience vasovagal syncope, in which your blood vessels are inappropriately dilated during specific situations, thus causing low blood pressure and syncope. Certain cardiac arrhythmias can cause low blood pressure and lead to syncope. It is possible you are experiencing seizures. It is not possible to know the cause based on the information provided. Therefore, I strongly encourage you to schedule an appointment with a primary care doctor.

Zocdoc Answers is for general informational purposes only and is not a substitute for professional medical advice. If you think you may have a medical emergency, call your doctor (in the United States) 911 immediately. Always seek the advice of your doctor before starting or changing treatment. Medical professionals who provide responses to health-related questions are intended third party beneficiaries with certain rights under Zocdoc’s Terms of Service.