There are several reasons why your gums might bleed. In most cases, oral health-related issues cause it. But it can also be a symptom of other health conditions. Dental causes include: Poor oral hygiene. Smoking. Gingivitis (early-stage gum disease). Periodontitis (moderate to advanced gum disease). Trench mouth (severe gum disease). Other causes include: Diabetes. Hormone changes during puberty, pregnancy or menopause. Vitamin K deficiency. Vitamin C deficiency or scurvy (a severe form of vitamin C deficiency). Blood-thinning medications (anticoagulants). Pernicious anemia. Thrombocytopenia. Hemophilia. Von Willebrand disease. Oral herpes. HIV/AIDS. Stress. Leukemia.