Unofficial Step 1 practice questions on basic science, spread over the systems of the content outline.
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Unofficial practice questions, not affiliated with the Federation of State Medical Boards and National Board of Medical Examiners. Bank checked October 10, 2026.
The real exam, as the USMLE program describes it
Length
Fourteen 30-minute blocks in one 8-hour testing session, for anyone testing on or after May 14, 2026. A block holds no more than 20 questions.
Breaks
At least 55 minutes of break time and an optional 5-minute tutorial. Finishing a block early adds to the break time.
Result
Pass or fail, as a recommendation. The percent of items needed varies from form to form; examinees typically must answer approximately 60 percent correctly.
Where
A test center, booked through the scheduling links on the exam page of usmle.org.
A newborn lies face up. When the examiner lets the supported head drop back for a moment, the arms move sideways with the palms up, then draw back to the body. By what age does this reflex normally go away?MedlinePlus Medical Encyclopedia, Moro reflex, opening and Considerations. Outline: USMLE Step 1, Human Development.
Blood and immune systems 7
A 3-year-old boy has repeated bacterial and fungal infections and granulomas. His phagocytes cannot make superoxide. Which enzyme complex is defective?MedlinePlus Genetics, Chronic granulomatous disease, Causes. Outline: USMLE Step 1, Blood & Lymphoreticular/Immune Systems.
A 6-year-old has anemia and repeated episodes of pain. His red cells carry hemoglobin S. The variant that causes this lies in the gene for which protein?MedlinePlus Genetics, Sickle cell disease, Causes. Outline: USMLE Step 1, Blood & Lymphoreticular/Immune Systems.
A 62-year-old woman has anemia because her intestine cannot absorb vitamin B12. Her stomach releases too little of the protein that binds the vitamin for absorption. Which protein is it?MedlinePlus Medical Encyclopedia, Pernicious anemia, Causes. Outline: USMLE Step 1, Blood & Lymphoreticular/Immune Systems.
Show all 60 questions (56 more)
Blood and immune systems, continued
A boy bleeds for hours after a tooth is pulled. Testing shows hemophilia A. Which protein is abnormal or in short supply?MedlinePlus Genetics, Hemophilia, Causes. Outline: USMLE Step 1, Blood & Lymphoreticular/Immune Systems.
A man with glucose-6-phosphate dehydrogenase deficiency develops hemolytic anemia during an infection. The missing enzyme normally protects red blood cells from what?MedlinePlus Genetics, Glucose-6-phosphate dehydrogenase deficiency, Causes. Outline: USMLE Step 1, Blood & Lymphoreticular/Immune Systems.
A traveler has anemia and fevers that return in cycles of 48 to 72 hours after a mosquito bite abroad. In this parasitic disease, where do the parasites first mature before they infect red blood cells?MedlinePlus Medical Encyclopedia, Malaria, Causes. Outline: USMLE Step 1, Blood & Lymphoreticular/Immune Systems.
A young boy has one bacterial infection after another and makes very few antibodies. In this X-linked recessive condition, B cells fail to develop. A variant in which gene is responsible?MedlinePlus Genetics, X-linked agammaglobulinemia, Causes and Inheritance. Outline: USMLE Step 1, Blood & Lymphoreticular/Immune Systems.
Behavioral health and nervous system 7
A 34-year-old woman has drooping eyelids and skeletal muscle weakness from an autoimmune disorder. In most affected people, the antibody targets which protein?MedlinePlus Genetics, Myasthenia gravis, Causes. Outline: USMLE Step 1, Behavioral Health & Nervous Systems/Special Senses.
A 42-year-old man has uncontrolled movements and declining thinking ability, as his father did. Testing finds 44 repeats of a DNA segment in the HTT gene. Which three-letter segment is repeated?MedlinePlus Genetics, Huntington's disease, Causes. Outline: USMLE Step 1, Behavioral Health & Nervous Systems/Special Senses.
A 68-year-old man has shaking and trouble walking from Parkinson disease. The brain cells that slowly die in this disease make which chemical?MedlinePlus Medical Encyclopedia, Parkinson disease, Causes. Outline: USMLE Step 1, Behavioral Health & Nervous Systems/Special Senses.
A man with alcohol use disorder has confusion, loss of muscle coordination and abnormal eye movements. A lack of which vitamin causes this brain disorder?MedlinePlus Medical Encyclopedia, Wernicke-Korsakoff syndrome, Causes and Symptoms. Outline: USMLE Step 1, Behavioral Health & Nervous Systems/Special Senses.
A woman with depression starts fluoxetine. The drug works by increasing the amount of which natural substance in the brain?MedlinePlus Drug Information, Fluoxetine, Why is this medication prescribed?. Outline: USMLE Step 1, Behavioral Health & Nervous Systems/Special Senses.
An infant develops normally for a few months, then loses motor skills. Variants in the HEXA gene are found. Which substance builds up to toxic levels in the neurons?MedlinePlus Genetics, Tay-Sachs disease, Causes. Outline: USMLE Step 1, Behavioral Health & Nervous Systems/Special Senses.
An unvaccinated farmer has severe muscle spasms days after soil got into a wound. How does the bacterial toxin cause the spasms?MedlinePlus Medical Encyclopedia, Tetanus, Causes. Outline: USMLE Step 1, Behavioral Health & Nervous Systems/Special Senses.
Musculoskeletal system and skin 6
A 4-year-old boy has progressive muscle weakness and wasting. A mutation in the DMD gene is found. Which protein, which helps stabilize and protect muscle fibers, is missing?MedlinePlus Genetics, Duchenne and Becker muscular dystrophy, Causes. Outline: USMLE Step 1, Musculoskeletal, Skin & Subcutaneous Tissue.
A 55-year-old man wakes with pain, swelling and warmth in one joint. He has gout. The crystals that inflame the joint form from a buildup of which substance?MedlinePlus Medical Encyclopedia, Gout, Causes. Outline: USMLE Step 1, Musculoskeletal, Skin & Subcutaneous Tissue.
A child's bones fracture easily. A COL1A1 mutation has reduced the amount of one protein, although the molecules made are normal. Which protein?MedlinePlus Genetics, Osteogenesis imperfecta, Causes. Outline: USMLE Step 1, Musculoskeletal, Skin & Subcutaneous Tissue.
A toddler who was only breastfed and gets little sunlight has soft, weak bones. A lack of which vitamin is the most likely cause?MedlinePlus Medical Encyclopedia, Rickets, Causes. Outline: USMLE Step 1, Musculoskeletal, Skin & Subcutaneous Tissue.
Mutations in the FBN1 gene cause Marfan syndrome. The fibrillin-1 protein binds to itself and to other molecules to form which threadlike structures of connective tissue?MedlinePlus Genetics, Marfan syndrome, Causes. Outline: USMLE Step 1, Musculoskeletal, Skin & Subcutaneous Tissue.
Two specific variants in the FGFR3 gene cause almost all cases of achondroplasia. What do they do to the FGFR3 protein?MedlinePlus Genetics, Achondroplasia, Causes. Outline: USMLE Step 1, Musculoskeletal, Skin & Subcutaneous Tissue.
Cardiovascular system 5
A 28-year-old has familial hypercholesterolemia with very high blood cholesterol. The most common cause is a change in the gene for which protein?MedlinePlus Genetics, Familial hypercholesterolemia, Causes. Outline: USMLE Step 1, Cardiovascular System.
A student listens to a healthy heart and hears "lub-DUB". Which event makes the first sound, the "lub"?National Heart, Lung, and Blood Institute, How the Heart Beats, Your heartbeat. Outline: USMLE Step 1, Cardiovascular System.
An infant with a bluish-purple skin color has tetralogy of Fallot. Which of these is one of its four classic defects?MedlinePlus Medical Encyclopedia, Tetralogy of Fallot, Causes. Outline: USMLE Step 1, Cardiovascular System.
Atorvastatin lowers the risk of heart attack by slowing how much cholesterol the body makes. To which class of medications does it belong?MedlinePlus Drug Information, Atorvastatin, Why is this medication prescribed?. Outline: USMLE Step 1, Cardiovascular System.
In a normal heartbeat the electrical signal slows slightly at one point, which gives the ventricles time to finish filling. Where does this happen?National Heart, Lung, and Blood Institute, How the Heart Beats, Electrical activity. Outline: USMLE Step 1, Cardiovascular System.
Respiratory and renal systems 8
A 7-year-old has had a chronic cough and nasal congestion since infancy, with repeated ear infections. His heart is on the right side of the chest. A DNAH5 variant is found. The protein this gene makes is part of which complex?MedlinePlus Genetics, Primary ciliary dyskinesia, Description and Causes. Outline: USMLE Step 1, Respiratory & Renal/Urinary Systems.
A 38-year-old has emphysema and variants in the SERPINA1 gene. Without enough of the protein this gene makes, which enzyme destroys the alveoli?MedlinePlus Genetics, Alpha-1 antitrypsin deficiency, Causes. Outline: USMLE Step 1, Respiratory & Renal/Urinary Systems.
A 40-year-old woman has kidneys full of fluid-filled cysts, as her father did. What is the inheritance pattern in most cases of this disease?MedlinePlus Genetics, Polycystic kidney disease, Inheritance. Outline: USMLE Step 1, Respiratory & Renal/Urinary Systems.
A baby born many weeks early has trouble breathing soon after birth. A lack of which substance in the lungs is the main cause?MedlinePlus Medical Encyclopedia, Neonatal respiratory distress syndrome, Causes. Outline: USMLE Step 1, Respiratory & Renal/Urinary Systems.
A boy has blood in his urine, progressive kidney disease and hearing loss. His glomeruli contain an abnormal version of which protein?MedlinePlus Genetics, Alport syndrome, Causes. Outline: USMLE Step 1, Respiratory & Renal/Urinary Systems.
A child with cystic fibrosis has thick, sticky mucus in the lungs and pancreas. The CFTR gene makes a channel that transports which ion?MedlinePlus Genetics, Cystic fibrosis, Causes. Outline: USMLE Step 1, Respiratory & Renal/Urinary Systems.
A man breathed in droplets from a coughing relative years ago. The lung infection stayed dormant and has now become active again. Which organism causes this disease?MedlinePlus Medical Encyclopedia, Pulmonary tuberculosis, Causes. Outline: USMLE Step 1, Respiratory & Renal/Urinary Systems.
As blood passes through a healthy glomerulus, water, wastes and small molecules pass into the tubule. What normally stays behind in the blood vessel?National Institute of Diabetes and Digestive and Kidney Diseases, Your Kidneys & How They Work, The glomerulus filters your blood. Outline: USMLE Step 1, Respiratory & Renal/Urinary Systems.
Gastrointestinal system 5
A 16-year-old has liver disease and psychiatric problems. Variants in the ATP7B gene are found. Which metal has accumulated in the liver and brain?MedlinePlus Genetics, Wilson disease, Description and Causes. Outline: USMLE Step 1, Gastrointestinal System.
A 17-year-old's routine blood test, taken after a day of fasting, shows raised unconjugated bilirubin. A change near the UGT1A1 gene is found. Which reaction does the affected liver enzyme perform?MedlinePlus Genetics, Gilbert syndrome, Description and Causes. Outline: USMLE Step 1, Gastrointestinal System.
A 50-year-old man has excess iron stored in his liver, heart and pancreas. He has mutations in the HFE gene. What is the basic defect?MedlinePlus Genetics, Hereditary hemochromatosis, Description and Causes. Outline: USMLE Step 1, Gastrointestinal System.
A man has an ulcer in the first part of his small intestine. He takes no pain medicines and does not smoke or drink. What is the most common cause of such ulcers?MedlinePlus Medical Encyclopedia, Peptic ulcer, Causes. Outline: USMLE Step 1, Gastrointestinal System.
A woman with celiac disease eats bread made from wheat. Her immune system reacts to the gluten by damaging which structures?MedlinePlus Medical Encyclopedia, Celiac disease - sprue, Causes. Outline: USMLE Step 1, Gastrointestinal System.
Reproductive and endocrine systems 8
A 9-year-old has high blood glucose from type 1 diabetes. In this autoimmune disorder, the body mistakenly attacks which cells?MedlinePlus Medical Encyclopedia, Type 1 diabetes, Causes. Outline: USMLE Step 1, Reproductive & Endocrine Systems.
A girl with Turner syndrome has monosomy X. Which error in cell division, during the formation of a parent's egg or sperm, can produce this?MedlinePlus Genetics, Turner syndrome, Inheritance. Outline: USMLE Step 1, Reproductive & Endocrine Systems.
A man is evaluated for infertility. His cells carry the usual X and Y chromosomes and one extra X chromosome. How is this chromosome pattern written?MedlinePlus Genetics, Klinefelter syndrome, Causes. Outline: USMLE Step 1, Reproductive & Endocrine Systems.
A newborn has 21-hydroxylase deficiency. This adrenal enzyme plays a role in producing which two hormones?MedlinePlus Genetics, 21-hydroxylase deficiency, Description and Causes. Outline: USMLE Step 1, Reproductive & Endocrine Systems.
A patient with type 2 diabetes starts metformin, a biguanide. Which of these is one of the ways it controls blood glucose?MedlinePlus Drug Information, Metformin, Why is this medication prescribed?. Outline: USMLE Step 1, Reproductive & Endocrine Systems.
A person with one X and one Y chromosome has external sex characteristics typical for females. Variants in the AR gene are found. Which protein does this gene make?MedlinePlus Genetics, Androgen insensitivity syndrome, Causes. Outline: USMLE Step 1, Reproductive & Endocrine Systems.
A woman has an overactive thyroid from Graves' disease. Her immune system makes an antibody called thyroid-stimulating immunoglobulin. What does it do?MedlinePlus Genetics, Graves' disease, Causes. Outline: USMLE Step 1, Reproductive & Endocrine Systems.
Autoimmune damage to the adrenal cortex leaves a patient short of its hormones. Which cortical hormone regulates sodium, water and potassium balance?MedlinePlus Medical Encyclopedia, Addison disease, Causes. Outline: USMLE Step 1, Reproductive & Endocrine Systems.
Multisystem processes 6
A boy with learning disabilities has more than 200 CGG repeats in the FMR1 gene. What is the inheritance pattern of this syndrome?MedlinePlus Genetics, Fragile X syndrome, Causes and Inheritance. Outline: USMLE Step 1, Multisystem Processes & Disorders.
A child has changes in skin coloring and tumors growing along nerves. The NF1 gene is mutated. How does its protein, neurofibromin, normally act?MedlinePlus Genetics, Neurofibromatosis type 1, Causes. Outline: USMLE Step 1, Multisystem Processes & Disorders.
A man who drinks heavily and eats poorly has diarrhea, confusion and scaly sores on sun-exposed skin. His diet most likely lacks which nutrient?MedlinePlus Medical Encyclopedia, Pellagra, Causes and Symptoms. Outline: USMLE Step 1, Multisystem Processes & Disorders.
A newborn has weak muscle tone and a characteristic facial appearance. What do most cases of this chromosomal condition result from?MedlinePlus Genetics, Down syndrome, Causes. Outline: USMLE Step 1, Multisystem Processes & Disorders.
Newborn screening is positive for phenylketonuria. Variants in the PAH gene have altered which enzyme?MedlinePlus Genetics, Phenylketonuria, Causes. Outline: USMLE Step 1, Multisystem Processes & Disorders.
Several relatives in one family have had colorectal cancer. A variant in MLH1 is found. What do MLH1 and the related MSH2 gene normally do?MedlinePlus Genetics, Lynch syndrome, Causes. Outline: USMLE Step 1, Multisystem Processes & Disorders.
Biostatistics and epidemiology 3
A new screening test is given to 200 people who have a disease and 300 who do not. It is positive in 160 of those with the disease and in 30 of those without. What is the sensitivity?CDC, Principles of Epidemiology in Public Health Practice, third edition (archived), Glossary, sensitivity. Outline: USMLE Step 1, Biostatistics & Epidemiology/Population Health.
In a cohort study, 30 of 200 smokers and 10 of 200 non-smokers develop a disease over ten years. What is the risk ratio for smokers compared with non-smokers?CDC, Principles of Epidemiology in Public Health Practice, third edition (archived), Lesson 3, Section 5, Risk ratio. Outline: USMLE Step 1, Biostatistics & Epidemiology/Population Health.
On July 1 a town of 10,000 people has 400 residents living with diabetes, 50 of them diagnosed in the past year. What is the point prevalence of diabetes on July 1?CDC, Principles of Epidemiology in Public Health Practice, third edition (archived), Lesson 3, Section 2, Prevalence. Outline: USMLE Step 1, Biostatistics & Epidemiology/Population Health.
Communication skills 4
A clinician and a patient are choosing between two reasonable treatments. In the SHARE Approach to shared decision-making, the dialogue explores the benefits, harms and risks of the options and what else?Agency for Healthcare Research and Quality, The SHARE Approach, opening paragraph. Outline: USMLE Step 1, Social Sciences: Communication and Interpersonal Skills.
A patient who prefers to speak Spanish comes to clinic with her bilingual 12-year-old son. The physician speaks only English. Who should interpret?Agency for Healthcare Research and Quality, Health Literacy Universal Precautions Toolkit, Tool 9: Address Language Differences, Use only acceptable language access services. Outline: USMLE Step 1, Social Sciences: Communication and Interpersonal Skills.
A physician explains a new diagnosis of high blood pressure to a patient who has trouble with medical terms. Which approach does the health literacy toolkit recommend?Agency for Healthcare Research and Quality, Health Literacy Universal Precautions Toolkit, Tool 4: Communicate Clearly, Key strategies. Outline: USMLE Step 1, Social Sciences: Communication and Interpersonal Skills.
A physician has just explained how to use a new inhaler. Which is the best way to check the patient's understanding?Agency for Healthcare Research and Quality, Health Literacy Universal Precautions Toolkit, Tool 5: Use the Teach-Back Method, Overview and Actions. Outline: USMLE Step 1, Social Sciences: Communication and Interpersonal Skills.
How this list was compiled: Our own questions, written to the Step 1 content outline and specifications of the USMLE program (https://www.usmle.org/exam-resources/step-1-materials/step-1-content-outline-and-specifications, read 2026-10-10). Its systems and their ranges: Human Development 1-3%, Blood & Lymphoreticular/Immune Systems 9-13%, Behavioral Health & Nervous Systems/Special Senses 10-14%, Musculoskeletal, Skin & Subcutaneous Tissue 8-12%, Cardiovascular System 7-11%, Respiratory & Renal/Urinary Systems 11-15%, Gastrointestinal System 6-10%, Reproductive & Endocrine Systems 12-16%, Multisystem Processes & Disorders 8-12%, Biostatistics & Epidemiology/Population Health 4-6%, Social Sciences: Communication and Interpersonal Skills 6-9%. The bank holds 1, 7, 7, 6, 5, 8, 5, 8, 6, 3 and 4 questions in that order, 60 in all. Every fact was read on 2026-10-10 in the public source the question names: MedlinePlus Genetics, the MedlinePlus Medical Encyclopedia and MedlinePlus Drug Information (National Library of Medicine), the National Heart, Lung, and Blood Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, the Agency for Healthcare Research and Quality and the archived CDC course Principles of Epidemiology in Public Health Practice. The three statistics answers are arithmetic on the numbers in the question. Licence: Questions, choices and explanations are original work of this site.
How it works
This free USMLE Step 1 practice test has 60 basic science questions of our own. It is unofficial, not affiliated with or endorsed by the Federation of State Medical Boards (FSMB) or the National Board of Medical Examiners (NBME).
Read the full guide
What the exam covers
The Step 1 content outline on usmle.org, read October 10, 2026, gives each system a range: reproductive and endocrine 12 to 16%, respiratory and renal 11 to 15%, behavioral health and nervous system 10 to 14%, down to human development at 1 to 3%. The 60 questions follow those shares.
Timing
Since May 14, 2026 the real exam is fourteen 30-minute blocks of no more than 20 questions. Exam mode asks 40 questions in 60 minutes: two blocks at that pace.
Where the answers come from
Each question names the public page its answer was read in: MedlinePlus, institutes of the National Institutes of Health, AHRQ and a CDC epidemiology course.
The real exam asks you to interpret graphs, tables and specimens. These questions are text only, with four choices and one right answer.
Questions and answers
Are these real Step 1 questions?
No. The exam's owners publish their own sample questions on usmle.org. This Step 1 practice test is a separate bank: none of its questions repeats or rewords one of theirs, and none comes from a review book.
How many questions are on Step 1?
Fourteen 30-minute blocks, each with no more than 20 questions, in one 8-hour session with at least 55 minutes of break time. That is the format since May 14, 2026, by the Step 1 page on usmle.org.
What score do you need to pass Step 1?
The USMLE program gives a pass or fail recommendation. The percent needed varies from form to form, and usmle.org says examinees usually need about 60 percent of items right. A result here forecasts nothing.
Can I take a practice session at a test center?
Not here. The exam's owners offer a practice session at a Prometric test center, to become familiar with a real test center, and the Step 1 materials page on usmle.org links to registration.