,FIRST AID FOR
THE®
USMLE
STEP 1
2021
TAO LE, MD, MHS VIKAS BHUSHAN, MD
Founder, ScholarRx Founder, First Aid for the USMLE Step 1
Associate Clinical Professor, Department of Medicine Boracay, Philippines
University of Louisville School of Medicine
MATTHEW SOCHAT, MD HUMOOD BOQAMBAR, MB BCh BAO
Physician, Hematology/Oncology Assistant Registrar, Department of Orthopedic Surgery
Southeastern Medical Oncology Center Farwaniya Hospital
KRISTINA DAMISCH, MD CONNIE QIU
University of Iowa Carver College of Medicine Lewis Katz School of Medicine at Temple University
Class of 2020 MD/PhD Candidate
JORDAN ABRAMS, MD CAROLINE COLEMAN, MD
Resident, Department of Anesthesiology, Resident, Department of Medicine
Perioperative and Pain Medicine Emory University School of Medicine
Mount Sinai West and Mount Sinai Morningside Hospitals
KIMBERLY KALLIANOS, MD
Assistant Professor, Department of Radiology and Biomedical Imaging
University of California, San Francisco School of Medicine
New York / Chicago / San Francisco / Athens / London / Madrid / Mexico City
Milan / New Delhi / Singapore / Sydney / Toronto
,First Aid for the® USMLE Step 1 2021: A Student-to-Student Guide
Copyright © 2021 by Tao Le and Vikas Bhushan. All rights reserved. Printed in the United States of America. Except as
permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distrib-
uted in any form or by any means, or stored in a data base or retrieval system, without the prior written permission of
the publisher.
Previous editions copyright © 1991 through 2020 by Tao Le and Vikas Bhushan. First edition copyright © 1990, 1989
by Vikas Bhushan, Jeffrey Hansen, and Edward Hon.
Photo and line art credits for this book begin on page 753 and are considered an extension of this copyright page.
Portions of this book identified with the symbol are copyright © USMLE-Rx.com (MedIQ Learning, LLC).
Portions of this book identified with the symbol are copyright © Dr. Richard Usatine.
Portions of this book identified with the symbol are under license from other third parties. Please refer to page 753
for a complete list of those image source attribution notices.
First Aid for the® is a registered trademark of McGraw Hill.
1 2 3 4 5 6 7 8 9 LMN 25 24 23 22 21 20
ISBN 978-1-260-46752-9
MHID 1-260-46752-X
Notice
Medicine is an ever-changing science. As new research and clinical experience broaden our knowledge,
changes in treatment and drug therapy are required. The authors and the publisher of this work have checked
with sources believed to be reliable in their efforts to provide information that is complete and generally in
accord with the standards accepted at the time of publication. However, in view of the possibility of human
error or changes in medical sciences, neither the authors nor the publisher nor any other party who has been
involved in the preparation or publication of this work warrants that the information contained herein is in
every respect accurate or complete, and they disclaim all responsibility for any errors or omissions or for the
results obtained from use of the information contained in this work. Readers are encouraged to confirm the
information contained herein with other sources. For example and in particular, readers are advised to check
the product information sheet included in the package of each drug they plan to administer to be certain
that the information contained in this work is accurate and that changes have not been made in the recom-
mended dose or in the contraindications for administration. This recommendation is of particular importance
in connection with new or infrequently used drugs.
This book was set in Electra LT Std by GW Inc.
The editors were Bob Boehringer and Christina M. Thomas.
Project management was provided by GW Inc.
The production supervisor was Jeffrey Herzich.
LSC Communications was printer and binder.
This book is printed on acid-free paper.
Copyright © 2021. Exclusive rights by McGraw Hill for manufacture and export. This book cannot be reexported from
the country to which it is consigned by McGraw Hill. The International Edition is not available in North America.
McGraw Hill books are available at special quantity discounts to use as premiums and sales promotions,
or for use in corporate training programs. To contact a representative please visit the Contact Us pages at
www.mhprofessional.com.
, Dedication
To all healthcare workers and first responders worldwide leading
the fight against COVID-19. We salute your ongoing efforts and
honor those who have lost their lives in service to others.
THE®
USMLE
STEP 1
2021
TAO LE, MD, MHS VIKAS BHUSHAN, MD
Founder, ScholarRx Founder, First Aid for the USMLE Step 1
Associate Clinical Professor, Department of Medicine Boracay, Philippines
University of Louisville School of Medicine
MATTHEW SOCHAT, MD HUMOOD BOQAMBAR, MB BCh BAO
Physician, Hematology/Oncology Assistant Registrar, Department of Orthopedic Surgery
Southeastern Medical Oncology Center Farwaniya Hospital
KRISTINA DAMISCH, MD CONNIE QIU
University of Iowa Carver College of Medicine Lewis Katz School of Medicine at Temple University
Class of 2020 MD/PhD Candidate
JORDAN ABRAMS, MD CAROLINE COLEMAN, MD
Resident, Department of Anesthesiology, Resident, Department of Medicine
Perioperative and Pain Medicine Emory University School of Medicine
Mount Sinai West and Mount Sinai Morningside Hospitals
KIMBERLY KALLIANOS, MD
Assistant Professor, Department of Radiology and Biomedical Imaging
University of California, San Francisco School of Medicine
New York / Chicago / San Francisco / Athens / London / Madrid / Mexico City
Milan / New Delhi / Singapore / Sydney / Toronto
,First Aid for the® USMLE Step 1 2021: A Student-to-Student Guide
Copyright © 2021 by Tao Le and Vikas Bhushan. All rights reserved. Printed in the United States of America. Except as
permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distrib-
uted in any form or by any means, or stored in a data base or retrieval system, without the prior written permission of
the publisher.
Previous editions copyright © 1991 through 2020 by Tao Le and Vikas Bhushan. First edition copyright © 1990, 1989
by Vikas Bhushan, Jeffrey Hansen, and Edward Hon.
Photo and line art credits for this book begin on page 753 and are considered an extension of this copyright page.
Portions of this book identified with the symbol are copyright © USMLE-Rx.com (MedIQ Learning, LLC).
Portions of this book identified with the symbol are copyright © Dr. Richard Usatine.
Portions of this book identified with the symbol are under license from other third parties. Please refer to page 753
for a complete list of those image source attribution notices.
First Aid for the® is a registered trademark of McGraw Hill.
1 2 3 4 5 6 7 8 9 LMN 25 24 23 22 21 20
ISBN 978-1-260-46752-9
MHID 1-260-46752-X
Notice
Medicine is an ever-changing science. As new research and clinical experience broaden our knowledge,
changes in treatment and drug therapy are required. The authors and the publisher of this work have checked
with sources believed to be reliable in their efforts to provide information that is complete and generally in
accord with the standards accepted at the time of publication. However, in view of the possibility of human
error or changes in medical sciences, neither the authors nor the publisher nor any other party who has been
involved in the preparation or publication of this work warrants that the information contained herein is in
every respect accurate or complete, and they disclaim all responsibility for any errors or omissions or for the
results obtained from use of the information contained in this work. Readers are encouraged to confirm the
information contained herein with other sources. For example and in particular, readers are advised to check
the product information sheet included in the package of each drug they plan to administer to be certain
that the information contained in this work is accurate and that changes have not been made in the recom-
mended dose or in the contraindications for administration. This recommendation is of particular importance
in connection with new or infrequently used drugs.
This book was set in Electra LT Std by GW Inc.
The editors were Bob Boehringer and Christina M. Thomas.
Project management was provided by GW Inc.
The production supervisor was Jeffrey Herzich.
LSC Communications was printer and binder.
This book is printed on acid-free paper.
Copyright © 2021. Exclusive rights by McGraw Hill for manufacture and export. This book cannot be reexported from
the country to which it is consigned by McGraw Hill. The International Edition is not available in North America.
McGraw Hill books are available at special quantity discounts to use as premiums and sales promotions,
or for use in corporate training programs. To contact a representative please visit the Contact Us pages at
www.mhprofessional.com.
, Dedication
To all healthcare workers and first responders worldwide leading
the fight against COVID-19. We salute your ongoing efforts and
honor those who have lost their lives in service to others.
