Is it possible for me to smoke marijuana and be also be on thyroid medication , if so what are the affects?

You could, but don't: Marijuana considered a gateway drug and its use leads to opiate abuse. Symptoms include the acute effects like: euphoria, relaxed inhibitions, increased appetite disoriented behavior, chronic use symptoms include: amotivational syndrome, aimless, uncommunicative. Withdrawal symptoms include: anorexia, insomnia, anxiety, depression. It can mask the benefits from thyroid medications.

Which thyroid med?: Hypothyroid patients have difficulty with cognition, fatigue and alertness. Mj will worsen those symptoms and make treatment more difficult. Hyperthyroid patients have difficulty with hypertension and tachycardia. Mj will worsen those symptoms. So best not to use mj if you have thyroid problems.