Definition and Symptoms -->
Anemia (/əˈniːmiə/; also spelled anaemia and anæmia) is usually defined as a decrease in amount of red blood cells (RBCs) or the amount of hemoglobin in the blood.[1][2] It can also be defined as a lowered ability of the blood to carry oxygen.[3] When anemia comes on slowly the symptoms are often vague and may include: feeling tired, weakness, shortness of breath or a poor ability to exercise. Anemia that comes on quickly often has greater symptoms which may include: confusion, feeling like one is going to pass out, and an increased desire to drink fluids. There needs to be significant anemia before a person becomes noticeably pale. There may be additional symptoms depending on the underlying cause.[4]
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’’’貧血’’’（{{lang-en|anemia, anaemia}}，{{lang-la|anæmia}}）通常定義為血液中[[紅血球]]或[[血紅素]]總數量下降的情形<ref>{{cite web |title=Anemia |url=http://www.merriam-webster.com/dictionary/anemia |website=http://www.merriam-webster.com/ |accessdate=2014-7-7}}</ref><ref>{{cite book |title=Stedman’s medical dictionary |date=2006 |publisher=Lippincott Williams & Wilkins|location=Philadelphia |isbn=9780781733908 |page=Anemia |edition=28th ed.}}</ref>；也可以被定義為血液攜帶[[氧氣]]能力下降的情況<ref>{{cite book |first1=[edited by] Bernadette F. Rodak |title=Hematology : clinical principles and applications|date=2007 |publisher=Saunders|location=Philadelphia |isbn=9781416030065 |page=220 |edition=3. ed.|url=http://books.google.ca/books?id=6sfacydDNsUC&pg=PA220}}</ref>。當貧血慢性發作時，其症狀往往不明顯，可能包含[[疲倦]]、虛弱、[[呼吸困難]]或活動能力下降；有時急性發作，就會出現較為強烈的症狀，可能包含{{link-en|意識不清|Decreased_level_of_consciousness}}、[[昏厥|感覺將要昏倒]]以及想喝更多水。在一個人{{link-en|面色蒼白|Pallor}}得很明顯之前，就已經有顯著的貧血狀況了。依據不同病因，可能會出現額外的症狀<ref name=EBM2013>{{cite journal |last1=Janz |first1=TG |last2=Johnson |first2=RL |last3=Rubenstein |first3=SD|title=Anemia in the emergency department: evaluation and treatment. |journal=Emergency medicine practice |date=Nov 2013 |volume=15 |issue=11 |pages=1-15; quiz 15-6 |pmid=24716235}}</ref>。
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There are three main types of anemia, that due to blood loss, that due to decreased red blood cell production, and that due to increased red blood cell breakdown. Causes of blood loss include trauma and gastrointestinal bleeding among others. Causes of decreased production include iron deficiency, a lack of vitamin B12,thalassemia and a number of neoplasms of the bone marrow among others. Causes of increased breakdown include a number of genetic conditions such as sickle cell anemia, infections like malaria and some autoimmune diseases among others. It can also be classified based on the size of red blood cells and amount of hemoglobin in each cell. If the cells are small it is microcytic anemia, if they are large it is macrocytic anemia and if they are normal sized it is normocytic anemia. Diagnosis in men is based on a hemoglobin of less than 130 to 140 g/L (13 to 14 g/dL) while in women it must be less 120 to 130 g/L (12 to 13 g/dL).[4][5] Further testing is then required to determine the cause.[4]
<!-- 病因與診斷 -->
貧血的原因總共分為三種主要類型：一為[[失血]]；二為紅血球製造數量下降；三為紅血球細胞分解增加<!-- <ref name=EBM2013/> -->。失血可能是由於[[創傷]]以及[[消化道出血]]等；紅血球製造減少的原因包括[[缺鐵|鐵質缺乏]]、[[維生素B12缺乏症]]、[[地中海貧血|地中海型貧血]]、以及各種[[骨髓相關的腫瘤]]等等<!-- <ref name=EBM2013/> -->。造成紅血球分解增加的原因包括基因上的異常（例如[[鐮刀型紅血球疾病|鐮刀型貧血]]）、感染（例如[[瘧疾]]）、以及自體免疫性疾病<!-- <ref name=EBM2013/> -->。貧血也可以依[[紅血球的大小]]及[[每個紅血球中的血紅素量]]進行分類<!-- <ref name=EBM2013/> -->。如果紅血球較正常小，則稱為[[小球性貧血]]；如果較正常大則是[[巨球性貧血]]；如果大小在正常範圍內則屬於[[正常血球性貧血]]<!-- <ref name=EBM2013/> -->。診斷標準在男性是血紅素低於130-140 g/L（13-14 g/dL），但是在女性時必須低於120-130 g/L（12-13 g/dL）<ref name=EBM2013/><ref name=Smith2010>{{cite journal |last1=Smith RE |first1=Jr |title=The clinical and economic burden of anemia. |journal=The American journal of managed care |date=2010-3 |volume=16 Suppl Issues |pages=S59-66 |pmid=20297873}}</ref>。需要更進一步的測試才能知道病因<ref name=EBM2013/>。
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Certain groups of individuals, such as pregnant people, benefit from the use of iron pills for prevention.[4][6] Dietary supplementation, without determining the specific cause, is not recommended The use of blood transfusions is typically based on a persons signs and symptoms.[4] In those without symptoms they are not recommended unless hemoglobin levels are less than 60 to 80 g/L (6 to 8 g/dL).[4][7] These recommendations may also apply to some people with acute bleeding.[4]Erythropoiesis-stimulating medications are only recommended in those with severe anemia.[7]
<!-- 預防與治療 -->
對部分族群而言───比方說孕婦───服用{{link-en|鐵劑|iron pills}}一類的{{link-en|營養補充品|Dietary supplements}}對預防貧血是有幫助的<ref name=EBM2013/><ref>{{cite journal |last1=Bhutta |first1=ZA |last2=Das |first2=JK |last3=Rizvi |first3=A |last4=Gaffey |first4=MF |last5=Walker |first5=N |last6=Horton |first6=S |last7=Webb |first7=P |last8=Lartey |first8=A |last9=Black |first9=RE |last10=Lancet Nutrition Interventions Review |first10=Group |last11=Maternal and Child Nutrition Study |first11=Group|title=Evidence-based interventions for improvement of maternal and child nutrition: what can be done and at what cost?|journal=Lancet|date=2013-8-3 |volume=382 |issue=9890 |pages=452-77 |pmid=23746776}}</ref>，但是並不推薦用在貧血原因尚不明的病人<!-- .<ref name=EBM2013/> -->。進行輸血治療的時機一般視症狀而定<ref name=EBM2013/>。對於沒有症狀的病人而言，血紅素值只要不低於60-80 g/L（6-8 g/dL）就不建議給予輸血<ref name=EBM2013/><ref name=Amir2013/>，這樣的標準也可以套用在部分急性出血的病人身上<ref name=EBM2013/>。紅血球生成刺激劑一般只建議用於嚴重貧血的患者身上<ref name=Amir2013>{{cite journal |last1=Qaseem |first1=A |last2=Humphrey |first2=LL |last3=Fitterman |first3=N |last4=Starkey |first4=M |last5=Shekelle |first5=P |last6=Clinical Guidelines Committee of the American College of |first6=Physicians |title=Treatment of anemia in patients with heart disease: a clinical practice guideline from the American College of Physicians. |journal=Annals of internal medicine |date= 2013-12-3 |volume=159 |issue=11 |pages=770-9 |pmid=24297193}}</ref>。
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Anemia is the most common disorder of the blood with it affecting about a quarter of people globally.[4] Iron-deficiency anemia affects nearly 1 billion.[8] It is more common in females than males[8] among children, during pregnancy and in the elderly.[4] Anemia increases costs of medical care and lowers a person’s productivity through a decreased ability to work.[5] The name is derived from Ancient Greek: ἀναιμία anaimia, meaning "lack of blood", from ἀν- an-, "not" + αἷμαhaima, "blood".[9]
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貧血是血液疾病中最常見的一種，影響了全球四分之一的人口<ref name=EBM2013/>。全世界大約有十億人患有缺鐵性貧血<ref name=LancetEpi2012>{{cite journal |last1=Vos |first1=T |last2=Flaxman |first2=AD |last3=Naghavi |first3=M |last4=Lozano |first4=R |last5=Michaud |first5=C |last6=Ezzati |first6=M |last7=Shibuya |first7=K |last8=Salomon |first8=JA |last9=Abda lla|first9=S |last10=Aboyans |first10=Victor |last11=Abraham |first11=Jerry |last12=Ackerman |first12=Ilana |last13=Aggarwal |first13=Rakesh |last14=Ahn |first14=Stephanie Y |last15=Ali |first15=Mohammed K |last16=Almazroa |first16=Mohammad A |last17=Alvarado |first17=Miriam |last18=Anderson |first18=H Ross |last19=Anderson |first19=Laurie M |last20=Andrews |first20=Kathryn G |last21=Atkinson |first21=Charles |last22=Baddour |first22=Larry M |last23=Bahalim |first23=Adil N |last24=Barker-Collo |first24=Suzanne |last25=Barrero |first25=Lope H |last26=Bartels |first26=David H |last27=Basáñez |first27=Maria-Gloria |last28=Baxter |first28=Amanda |last29=Bell |first29=Michelle L |last30=Benjamin |first30=Emelia J |title=Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010 |journal=Lancet |date=Dec 15, 2012 |volume=380 |issue=9859 |pages=2163–96 |pmid=23245607 |doi=10.1016/S0140-6736(12)61729-2 |display-authors=8}}</ref>。女性比男性更容易患病<ref name=LancetEpi2012/>，而孩童、孕婦以及年長者也較容易患病<ref name=EBM2013/>。貧血會增加醫療照護的成本，也會讓患者失去工作的能力而降低其生產力<ref name=Smith2010/>。其英文名源自古希臘文：「ἀναιμία(anaimia)」，字根為「ἀν- (an-)，否定」，以及「αἷμα(haima)，血液」<ref>{{cite web|title=anaemia |url=http://dictionary.reference.com/browse/anaemia |website=Dictionary.com |accessdate=2014-7-7}}</ref>。
| 英文 | 中文 |
| blood loss | 失血 |
| blood transfusion | 輸血 |
| iron pill | 鐵劑 |
| anemia | 貧血 |
| red blood cell | 紅血球 |
| hemoglobin | 血紅素 |
| trauma | 創傷 |