缺铁性贫血指的是因为缺乏铁质所产生的贫血，而贫血是指红血球细胞数量或血液中的血红素下降。一般贫血的产生影响的速度较缓慢，所以症状通常较不明显，其中症状包括感到疲倦、无力、呼吸急促或是运动能力下降等等。而相反的是，急性的贫血通常会有较严重的症状，可能会意识浑沌或有快要昏厥的感觉，并且感到口渴。若非十分严重的贫血，否则一般人不会有脸色苍白的现象。其他症状表现则常因成因不同而有所差异。

缺铁性贫血是由于从饮食摄取的铁质不足，或是身体吸收铁质不良所导致，也有可能是失血导致的铁质流失所引起。而出血的位置可能包括小肠、子宫或是泌尿道。就开发中国家的孩童而言，缺铁性贫血最常见的原因为寄生虫感染。寄生虫会造成肠道出血，但粪便中并不总是能明显发现。在未开发国家中，疟疾、钩虫和维他命A缺少是三个造成怀孕期间贫血的原因。在超过50岁的女性中，缺血性贫血最主要是慢性肠胃出血，其背后的原因与寄生虫感染无关，而是因为胃溃疡、十二指肠溃疡或是消化道癌症等因素。

Iron-deficiency anemia, also spelled iron deficiency anaemia, is anemia caused by not enough iron. Anemia is defined as a decrease in the amount of red blood cells (RBCs) or hemoglobin in the blood. When anemia comes on slowly, the symptoms are often vague and may include feeling tired, weakness, shortness of breath or 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 increased thirst. There needs to be significant anemia before a person becomes noticeably pale. There may be additional symptoms depending on the underlying cause.