Gingivitis or Periodontal Disease: This condition is common and can cause oral bleeding, especially if the patient has poor dental hygiene. The low hemoglobin could be a result of chronic blood loss over time.

Vitamin Deficiency (e.g., Vitamin C or K): Deficiencies in these vitamins can lead to bleeding gums and other bleeding tendencies, potentially causing low hemoglobin due to chronic blood loss.
Platelet Disorders (e.g., Thrombocytopenia): Conditions affecting platelet count or function can lead to bleeding, including oral bleeding, and if severe, could contribute to low hemoglobin levels.
Anticoagulant Therapy: Patients on anticoagulants are at an increased risk of bleeding, including oral bleeding, which could lead to low hemoglobin if the bleeding is significant.

Leukemia: Although less common, leukemia can cause bleeding due to bone marrow suppression affecting platelet production. It's crucial to consider this diagnosis to avoid missing a potentially life-threatening condition.
Bleeding Disorders (e.g., Hemophilia): While rare, these disorders can cause significant bleeding, including oral bleeding, and it's critical to identify them early for appropriate management.
Gastrointestinal Bleeding: Although the primary symptom is oral bleeding, it's essential to consider that the bleeding could be originating from the gastrointestinal tract, especially if the patient has other symptoms like black stools or abdominal pain.

Von Willebrand Disease: A genetic disorder that affects blood clotting, which could lead to oral bleeding and potentially low hemoglobin if the bleeding is recurrent or significant.
Amyloidosis: A condition where abnormal proteins (amyloid) accumulate in organs, potentially affecting the blood vessels and leading to bleeding, including oral bleeding.
Hereditary Hemorrhagic Telangiectasia (Osler-Weber-Rendu Syndrome): A rare genetic disorder characterized by the formation of abnormal blood vessels, which can lead to bleeding, including oral bleeding.