All of the soluble compounds of barium are poisonous when taken by mouth. Although insoluble, barium carbonate is extremely toxic, so as the chloride.

The barium ion is a muscle stimulant being very toxic to the heart and may cause ventricular fibrillation. Symptoms of barium poisoning are excessive salivation, convulsive tremors, rapid pulse, high blood pressure, paralysis of the arm and leg, hemorrhage and eventually cyanosis and death.

The antidote for ingested poisonous barium compounds is to drink a solution of sodium sulfate which converts the barium to the insoluble harmless barium sulfate.