What are the symptoms of carbon monoxide poisoning? Unfortunately, the symptoms caused by carboxyhemoglobin saturation are easily overlooked because they they tend to be flu-like. With mild exposure, most people experience headaches, fatigue and nausea. Medium exposure could cause a severe throbbing headache, drowsiness, disorientation, confusion and an accelerated heart rate. Extreme exposure can lead to unconsciousness, convulsions, cardiorespiratory failure, coma and possibly death.