Taking calcium tablets generally does not cause mouth ulcers, the occurrence of mouth ulcers may be related to immune factors, systemic disease factors, etc., as follows. 1. Immune factors: the occurrence of mouth ulcers may be related to autoimmunity, abnormal T-cell-mediated immune response, abnormal humoral immunity. 2. Systemic disease factors: mainly by affecting the immune system and cause disease, may be related to gastric ulcer, duodenal ulcer, ulcerative colitis, restrictive enteritis, hepatitis B or C and other diseases. The occurrence of mouth ulcers may also be related to other factors. If the symptoms of mouth ulcers are serious, prolonged or recurring frequently, it is recommended to go to the hospital in time to receive early professional treatment.