Complex sentence: The cause of chronic blood loss should all be considered, according to the patient's sex, age, and history, and anemia without an attributable underlying cause is sufficient for an urgent referral to exclude underlying malignancy.
Split into simpler sentences: The cause of chronic blood loss should be considered, according to the patient's sex, age, and history. Anemia without an attributable underlying cause is sufficient for an urgent referral to exclude underlying malignancy.