Would a full blood count show any kind of disease in the body?

Not every kind: While lab work, including a complete blood count (cbc), can help suggest and/or diagnose some diseases, many disorders do not show up in lab tests, especially early on. Labwork should only be ordered for age/gender appropriate screening, or if a patient's history and/or physical exam suggests a possible disease/condition/diagnosis which specific labwork would help confirm or rule out.