No, Delta 8 THC will not cause an overdose and it isn't poisonous to adults. However, you can experience negative side effects, such as vomiting or dizziness. You typically don't hear about Delta 8 THC or CBD overdoses because fatal overdoses don't occur as a result of consuming cannabinoids. Having said that, you have to be careful what other harmful chemicals are in your product. For example, vitamin E acetate in vape cartridges is linked to a deadly lung illness when inhaled. Quality products will not use vitamin E acetate.