What Is Internal Medicine? (2024)

Internal medicine doctors specialize in preventing, diagnosing, and treating a wide variety of diseases and other health issues that affect adults. They are experts in health promotion, disease prevention, and the care of problems both simple and complex, acute and chronic.

Internal medicine doctors apply research-based knowledge and clinical expertise to promote wellness and to diagnose and treat adults experiencing a very broad range of health concerns and diseases — from cardiovascular disease, infectious disease, gastrointestinal problems, and sports injuries to diabetes, age-related concerns, lung disease, and more.

Also called internists or general internists, internal medicine physicians often care for people with complex, chronic, and multisystem disorders.

Based on their subspecialties and their patients’ medical conditions, needs, and goals, internists may refer patients to (and partner with) physicians in other medical specialties, such as cardiologists, surgeons, and OB/GYN doctors.

Specialized Training

Internal medicine physicians are medical doctors (MDs) or doctors of osteopathic medicine (DOs). After medical school, trainees complete at least three years of residency training in an ACGME-accredited program, during which they focus on primary care medicine and hospital medicine, and are exposed to a variety of subspecialty disciplines.

Internal medicine training includes general medical education, as well as time spent rotating among a variety of inpatient and outpatient subspecialty clinics, where trainees gain experience working in areas that include:

• Adolescent medicine*
• Adult congenital heart disease*
• Advanced heart failure and transplant cardiology*
• Allergy and immunology (immune system)
• Cardiovascular disease* (heart and vascular system)
• Clinical cardiac electrophysiology* (heart-rhythm disorders)
• Critical care medicine*
• Dermatology (skin)
• Endocrinology, diabetes, and metabolism* (diabetes and other glandular and metabolic disorders)
• Gastroenterology* (gastrointestinal system, liver, and gallbladder)
• Geriatric medicine* (care of older patients)
• Hematology* (conditions of the blood, spleen, and lymph)
• Hospice and palliative medicine* (prevention and relief of suffering in people with life-limiting illnesses)
• Infectious disease* (bacterial, viral, fungal, and parasitic infections)
• Interventional cardiology* (minimally invasive diagnosis and care of cardiovascular conditions)
• Medical oncology* (chemotherapy and other drugs and agents to treat cancer)
• Nephrology* (kidneys)
• Neurocritical care* (life-threatening brain and nervous-system conditions)
• Neurology
• Oncology* (cancer)
• Ophthalmology
• Otolaryngology (ear, nose, and throat)
• Psychiatry (mental, emotional, and behavioral)
• Pulmonary disease* (lungs and respiratory system)
• Rheumatology* (diseases of the joints, muscles, and connective tissues)
• Sleep medicine*
• Sports medicine*
• Transplant hepatology (care surrounding liver transplantation)*
• Non-surgical orthopedics (musculoskeletal system)
• Rehabilitation medicine
• Women’s health*

*Board-certifiable internal medicine subspecialty

Internal medicine trainees spend much of their three years caring for hospitalized patients, with at least three months in intensive/critical care settings, as well as caring for patients in outpatient settings.

Many internal medicine doctors have a particular subspecialty. To gain expertise in those subspecialties, students complete an additional one to three years of fellowship training after a required three-year internal medicine residency.

Differences Between Internal Medicine Doctors and Family Medicine Doctors

Although they are both primary care doctors — and the terms are often used interchangeably — internal medicine physicians are not the same as family medicine physicians.

One of the biggest differences between the two specialties is that internal medicine specialists care for only adults, and family medicine physicians see both children and adults.

The American College of Physicians explains the unique differences in training and scope of care.

Internal Medicine

• Precise diagnoses of and prompt treatment for a broad range of symptoms and diseases
• Expertise in conditions that affect any of the body's systems
• Guidance, counseling, and preventive interventions for improved overall health
• Life-long comprehensive care of chronic conditions and palliative care
• Care for mental health disorders, such as depression and anxiety caused by abnormal activities in the brain, a chronic disease, or hormonal imbalances

Internists work in a variety of inpatient and outpatient settings — from hospitals, rehabilitation centers, and long-term care facilities to private practices, academic centers, and specialized outpatient centers.

Family Medicine

Family physicians can treat a full range of medical issues and provide acute, chronic, and wellness services for patients.

Residency programs differ, but all family physician trainees must spend several months training in obstetrics, pediatrics, general surgery, emergency medicine, and inpatient hospital care (including critical care) settings, according to the American Academy of Family Physicians.

After their residencies, many family medicine doctors choose to pursue fellowship training in specialties such as addiction medicine, sports medicine, or geriatrics.

Treating a Broad Range of Internal Medicine Conditions

Internal medicine doctors diagnose, manage, and treat a very wide variety of conditions — from the common and simple to the rare and complex.

They include diseases, infections, injuries, and other conditions affecting the heart, blood, kidneys, joints, and the digestive, respiratory, and vascular systems, such as:

• Allergies, including allergic rhinitis; angioedema (“hives”), and food allergies
• Birth control, including emergency contraception
• Bleeding and clotting disorders, including hemophilia, sickle cell disease, thrombotic thrombocytopenic purpura (TTP), intravascular coagulation, and von Willebrand disease
• Cardiac (heart) issues, including coronary artery disease; angina; pericarditis; heart defects; heart failure; arrhythmias such as atrial fibrillation and tachycardia; and complications of heart attack, stroke, and transient ischemic attack (TIA)
• Cognitive concerns, including cognitive impairment and dementia
• Dermatologic (skin) issues, including abscesses; cysts; cellulitis; skin cancer; and acne
• Ear, nose, and throat problems, including sinusitis; pharyngitis (sore throat); rhinitis; strep throat; otitis; and vertigo
• Endocrine conditions, including thyroid disease; electrolyte disorders; Cushing's syndrome; adrenal insufficiency; and diabetes and related complications, such as ketoacidosis and hyperglycemic state
• Gastrointestinal problems, including infections; bleeding; inflammatory bowel disease; colitis and Crohn’s disease; gastroenteritis; esophageal disease; ingested foreign bodies; food impaction; narrowing (stenosis) and blockages (ischemia); difficulty swallowing (dysphagia); anal fissure; acid peptic disease; diverticulitis and diverticulosis; peptic ulcers; pancreatitis; liver disease; cholecystitis; and cholangitis
• Hypertension (high blood pressure) and related complications, including hypertensive retinopathy and hypertensive encephalopathy
• Infections, including Lyme disease; infections of shunts and other implanted devices; soft-tissue infections; bacterial peritonitis; staphylococcal and streptococcal infections; toxic shock syndrome; non-HIV viral infections; and clostridioides difficile (“c. diff”)
• Kidney conditions, including chronic kidney disease; acute kidney injury; pre-renal disease; kidney stones; tubular necrosis; and hydronephrosis
• Liver disease, including cirrhosis; fatty liver; hepatitis; and hepatic encephalopathy
• Men’s health, including prostate disease and erectile dysfunction
• Metabolic conditions such as metabolic alkalosis; metabolic acidosis; and metabolic mineral and bone disease
• Neurologic conditions, including headaches; migraine; Bell’s palsy; meningitis; encephalitis; epilepsy; neuromuscular disease; and peripheral nerve and muscle diseases, such as neuropathies
• Non-surgical orthopedic issues, including strains, sprains, minor breaks, and other injuries; and joint pain and inflammation
• Pain, including acute pain; chronic pain; pain related to cancer and other conditions
• Pulmonary (lung and respiratory) issues, including bronchitis and other infections; asthma; pneumonia; trouble breathing; foreign bodies in the airway; chronic obstructive pulmonary disease (COPD); pneumothorax; and pulmonary embolism (blood clot)
• Urinary health, including urinary stones; bladder issues; and urinary tract infections
• Vascular (blood flow) conditions, including venous thrombosis; peripheral vascular disease; and syncope (fainting)
• Women’s health, including well-woman care and care for obstetric and gynecologic (OB/GYN) issues

Internal Medicine Tests and Procedures

Internal medicine doctors, nurses, and other providers are trained to perform many types of tests and procedures — some to evaluate, diagnose, and monitor patients, others to manage or treat specific conditions.

Clinicians need experience, skill, and in many cases, additional training and medical credentials to perform these procedures — and to minimize patient discomfort, optimize outcomes, and reduce side effects.

Internal medicine specialists commonly perform and order tests and procedures that include:

• Venipuncture (“blood draw”) to test blood
• Arterial puncture to analyze blood gases
• Endotracheal intubation
• Flexible sigmoidoscopy
• Intravenous (IV) line insertion
• Nasogastric (NG) tube placement
• Urinary catheters placement

Some internists have been trained in more complex and/or invasive diagnostic and therapeutic procedures, such as thoracentesis, lumbar puncture, and paracentesis.
Categories and other types of tests and procedures an internist might perform or order include:

• Allergy: Skin testing, rhinoscopy
• Cardiology: Cardiac stress testing, echocardiograms
• Endocrinology: Thyroid biopsy, dynamic hormone testing, bone density testing
• Oropharyngeal cancer screening
• Pulmonary: Intubation and ventilator management, bronchoscopy, chest tube thoracostomy, tracheostomy placement
• Rheumatology: Joint aspiration and therapeutic injection

Internal medicine and many other medical specialties use ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) to guide invasive procedures. Flexible fiber-optic instruments may be used to access hard-to-reach areas of the body.

Professional Societies for Internal Medicine

To deliver the safest, most up-to-date patient care, internal medicine specialists must stay current on all aspects of their specialty. One way they do that is by being involved with professional organizations for internal medicine. Those include:

• Alliance for Academic Internal Medicine
• American Board of Internal Medicine
• American College of Physicians
• American Medical Association
• Society of General Internal Medicine
• Society of Hospital Medicine

News and Information on Internal Medicine

Scientists and clinicians make advances in all medical specialties virtually every day. Stay informed about current research, clinical offerings, and other news and information about internal medicine by visiting trusted online sources such as:

• Centers for Disease Control and Prevention
• Medline Plus® (National Library of Medicine)
• Websites of reputable academic medical centers

Websites of reputable specialty-specific organizations, such as the American Cancer Society, American Heart Association, and American Diabetes Association

Q&A with Aldo Arpaia, MD

Aldo Arpaia, MD, is a Castle Connolly Top Doctor in Staten Island, New York. An internal medicine doctor who subspecializes in emergency medicine, Dr. Arpaia is affiliated with Staten Island University Hospital.

Q: How do you encourage people to make lifestyle adjustments that will improve their present and future health?
A: I believe it starts with getting patients to understand and buy into important lifestyle changes — and trying to reinforce that at every visit.

To improve their present and future health, patients should keep in mind that living an active lifestyle, eating a healthy diet, and refraining from tobacco and excessive alcohol use do indeed improve outcomes.

In addition, statin therapy, when indicated, can help slow the progression of coronary artery disease. And patients under 45 should consider being vaccinated against human papillomavirus (HPV).

Q: What are a few valuable diagnostic tests and procedures commonly used by internal medicine doctors?
A: There are a number of prudent and timely diagnostic tools at the internist’s disposal that have value and can improve the quality of care.

With the rise in the incidence of head and neck cancers, internists are on the front lines of oropharyngeal cancer screening.

Another is non-invasive coronary artery calcium scanning and scoring. Calcium scoring helps us determine the atherosclerotic load in asymptomatic patients at increased risk for heart disease and treat those people more aggressively.

Q: If someone has an internist, does s/he need to see any other types of doctors?
A: It’s important that patients have on their health teams specialists appropriate to their specific health needs.

For example, women should have gynecologists, heart patients should have cardiologists, and people with cancer should have oncologists.