There are several factors that can disqualify someone from joining the military, including medical conditions, criminal history, age, physical fitness, and drug abuse. Here are some specific examples of disqualifying factors:

Medical Conditions:

• Blood and Blood-Forming Tissue Diseases, including anemia, hemorrhagic disorders, leukopenia, and immunodeficiency
• Diseases of the jaw or associated tissues that are not easily remediable, and will incapacitate the individual or otherwise prevent the satisfactory performance of duty
• Allergies
• Food allergies resulting in systemic symptoms

Criminal History:

• Currently under civil restraint like probation, incarceration, or parole
• Convicted of any domestic violence offense under the Lautenberg Amendment
• Any crimes of sexual nature

Physical Fitness:

• Un-united fractures, history of instability of a major joint, certain retained orthopedic fixation devices, severe scoliosis, or any condition that could interfere with daily participation in rigorous physical training or athletic programs, wearing of military equipment, or detract from military bearing and appearance

Mental Health:

• Personality, conduct or behavior disorders as evidenced by frequent encounters with law enforcement agencies, antisocial attitudes or behavior, which, while not sufficient cause for administrative rejection, are tangible evidence of impaired capacity to adapt to military service
• A history of depressive or anxiety symptoms may be considered for waiver if treatment has been completed and a period of convincing stability demonstrated without need for ongoing medication or psychotherapy. Those with unresolved mental health issues and those with prolonged/recurrent or more severe diagnoses are unlikely to be considered waivable

Its important to note that this is not an exhaustive list, and there may be other factors that can disqualify someone from joining the military. Additionally, some disqualifying factors may be waived in certain circumstances.