| ⇔, nl | normal |
| ↓ | decreased, decreasing, depressed, down |
| → | causes, results in, next |
| ± | possibly, consider |
| ♀ | female |
| ♂ | male |
| Δ | change in |
| 1,25(OH)2-D | 1,25-dihydroxy vitamin D |
| 2/2 | secondary to |
| 2,3-DPG | 2,3-diphosphoglycerol |
| 25(OH) D | 25-hydroxy vitamin D |
| 5′-NT | 5′-nucleotidase |
| 6-MP | 6-mercaptopurine |
| AAA | anti-actin antibody |
| A-aDO2 | alveolar–arterial oxygen tension difference |
| AAP | American Academy of Pediatrics |
| AAT | α1 antitrypsin |
| Ab | antibody |
| ABC | airway, breathing, circulation |
| abd | abdominal |
| ABER | auditory brainstem-evoked response |
| ABG | arterial blood gas |
| ABNL | abnormal |
| ABPA | allergic bronchopulmonary aspergillosis |
| ABR | auditory brainstem response |
| abx | antibiotics |
| AC | assist control |
| ACEI | angiotensin-converting enzyme inhibitor |
| ACL | anterior cruciate ligament |
| acL | anticardiolipin |
| ACOG | American College of Obstetricians and Gynecologists |
| ACS | acute chest syndrome |
| ACTH | adrenocorticotropic hormone |
| AD | autosomal dominant |
| ADA | adenosine deaminase |
| ADC | apparent diffusion coefficient |
| ADEM | acute disseminated encephalomyelitis |
| ADH | antidiuretic hormone |
| ADHD | attention deficit hyperactivity disorder |
| ADL | activity of daily living |
| AED | antiepileptic drug |
| AET | atrial ectopic tachycardia |
| AFB | acid-fast bacilli |
| AFI | amniotic fluid index |
| AFP | α-fetoprotein |
| AG | anion gap |
| Ag | antigen |
| AGE | acute gastroenteritis |
| AGEP | acute generalized erythematous pustulosis |
| AHA | American Heart Association |
| AHI | apnea-hypopnea index (number of apneas + hypopneas per hour on polysomnography) |
| AI | aortic insufficiency; autoimmune |
| AIDS | acquired immune deficiency syndrome |
| AIH | autoimmune hepatitis |
| AIHA | autoimmune hemolytic anemia |
| AIN | acute interstitial nephritis |
| AKA | alcoholic ketoacidosis |
| AKI | acute kidney injury |
| Al+++ | aluminum |
| Ala | alanine |
| ALCAPA | anomalous left coronary artery arising from the pulmonary artery |
| ALD | adrenoleukodystrophy |
| Alk Phos | alkaline phosphatase |
| ALL | acute lymphoblastic leukemia |
| ALP | alkaline phosphatase |
| ALT | alanine aminotransferase |
| ALTE | apparent life-threatening episode |
| AMA | antimitochondrial antibody |
| AML | acute myelogenous leukemia |
| AMMoL | acute myelomonocytic leukemia |
| amox | amoxicillin |
| amp | ampicillin |
| ampho B | amphotericin B |
| AN | anorexia nervosa |
| ANA | antinuclear antibody |
| ANCA | antineutrophil cytoplasmic antibody |
| ANLL | acute nonlymphoblastic leukemia |
| anti-dsDNA Ab | anti-double stranded DNA antibody |
| anti-GAD Ab | anti-glutamic acid decarboxylase antibodies |
| anti-LC1 Ab | anti-liver cytosol-antibody |
| anti-LKM1 Ab | anti-liver/kidney microsome antibody |
| anti-LKM-1 | antibodies to liver/kidney microsomes |
| anti-SLA/LPAb | anti-soluble liver/liver pancreas antigen antibody |
| anti-TPOAb | anti-thyroid peroxidase antibodies |
| AOM | acute otitis media |
| AP | anterior posterior; aortopulmonary |
| APC | antigen-presenting cell |
| APTT | activated partial thromboplastin time |
| AR | aortic regurgitation; autosomal recessive |
| ARB | angiotensin receptor blocker |
| ARDS | acute respiratory distress syndrome |
| ARF | acute renal failure |
| AROM | artificial rupture of membranes |
| ARR | absolute risk reduction |
| ARVC | arrhythmogenic right ventricular cardiomyopathy |
| AS | aortic stenosis |
| ASA | aminosalicylic acid (aspirin) |
| ASD | atrial septal defect |
| ASMA | anti–smooth muscle antibody |
| Asp | aspartate |
| AST | aspartate aminotransferase |
| asx | asymptomatic |
| ATFL | anterior talofibular ligament |
| AT-II | angiotensin-II |
| ATN | acute tubular necrosis |
| ATP | adenosine triphosphate |
| ATRA | all trans retinoic acid |
| AUS | abdominal ultrasound |
| AV | arteriovenous; atrioventricular |
| AVB | atrioventricular block |
| AVCD | atrioventricular canal defect |
| AVM | arteriovenous malformation |
| AVN | avascular necrosis |
| AVP | arginine vasopressin |
| AXR | abdominal X-ray |
| BA | bone age |
| BAL | British antilewisite; bronchoalveolar lavage |
| BAS | balloon atrial septostomy |
| BCG | bacillus Calmette-Guérin |
| BCx | blood culture |
| BDG | bidirectional Glenn |
| BE | barium enema |
| β-HCG | beta human chorionic gonadotropin |
| BG | blood glucose |
| BID | twice daily |
| BiPAP | bilevel positive airway pressure |
| B/L | bilateral |
| BLS | basic life support |
| BM | bowel movement |
| BMA | bone marrow aspirate |
| BMD | Becker muscular ... |