 There are many conditions to be considered in the differential diagnosis of carbon monoxide poisoning . The earliest symptoms , especially from low level exposures , are often non @-@ specific and readily confused with other illnesses , typically flu @-@ like viral syndromes , depression , chronic fatigue syndrome , chest pain , and migraine or other headaches . Carbon monoxide has been called a " great <unk> " due to the presentation of poisoning being diverse and nonspecific . Other conditions included in the differential diagnosis include acute respiratory distress syndrome , altitude sickness , lactic acidosis , diabetic ketoacidosis , meningitis , methemoglobinemia , or opioid or toxic alcohol poisoning . 
