BACKGROUND Iron deficiency(ID) causes approximately half of all anemia cases worldwide, a moderate degree of iron-deficiency anemia(IDA) affected approximately 610 million people worldwide or 8.8% of the population. It is slightly more common in female (9.9%) than males (7.8%). In 2013, anemia due to iron deficiency resulted in about 183,000 deaths. IDA is an urgent problem to be solved.

Iron deficiency anemia(IDA) is anemia due to not enough iron. Anemia is defined as a decrease in the amount of red blood cells (RBCs) or hemoglobin in the blood. It is caused by insufficient dietary intake and absorption of iron, or iron loss from bleeding. In babies and adolescents, rapid growth may outpace dietary intake of iron, and result in deficiency without disease or grossly abnormal diet. In women of childbearing age, heavy or long menstrual periods can also cause mild iron-deficiency anemia. Anemia is sometimes treatable, but certain types of anemia may be lifelong. If the cause is dietary iron deficiency, eating more iron-rich foods, such as beans, lentils or red meat, or taking iron supplements will usually correct the anemia.

In clinic, IDA clinically divided into three stages: ID, iron deficiency erythropoiesis (iron deficiency erythropoiesis, IDE) and IDA. The first stage is the reduction of iron storage, and there is a history of inadequate iron absorption; the second stage is the IDE, in addition to iron reduction or lack of external storage, transferrin is also reduced, the intake of iron in red blood cells is reduced compared to normal condition at this time; IDA is the last stage of iron deficiency. If the patients are diagnosed with ID and this condition can be corrected by diet therapy; if it reaches the IDA criteria, it's need to take iron orally and improve symptoms as soon as possible, but the most important is to find the cause of iron deficiency. Ferrous succinate is commonly used to treat IDA in clinic, mainly absorbed in the duodenum and proximal jejunum in the form of ferrous iron. In health people, 5% to 10% of the iron are absorbed after taken orally. the absorption proportion is increased to 20%\~30% in IDA patients. After absorbed, ferrous iron can bind to transferrin and enter the blood circulation, and then involve in the production of red blood cells as raw materials. In clinical practice, the doctor will prescribe ferrous succinate with or without vitamin C according to their own preferences. Vitamin C Involves in many biological processes in vivo, such as, collagen formation, tissue repair, the synthesis of phenylalanine, tyrosine, metabolism of folic acid, iron and maintains vascular integrity. Researchers have shown that increased iron intake with vitamin C can prevent anemia,the application of vitamin C can reduce the toxicity symptoms in genotoxic caused by ferric iron, it demonstrates that vitamin C is safe when combined with ferrous succinate. In theory, only the divalent iron can be absorbed in the duodenum and upper jejunum, vitamin C can oxidize ferric iron into divalent iron and maintains a certain degree of acidity in the intestine, and then promotes the absorption of iron. However, the feasibility in theory can not represent the clinical practice. So it's necessary to explore the efficacy and safety of vitamin C for iron supplementation in adult IDA patients through randomized controlled trial(RCT).

PROCEDURE Before the start of this study, the manila envelope is used to carry out the random allocation scheme, different treatment options are randomly loaded into the envelope according to the randomization generated by Stata 11.0 software. In terms of the inclusion criteria, We write the serial number of patients on the envelope after signing informed consent form and give different treatments according to the internal treatment option in envelope. In addition to the above treatment, increased intake of protein, calcium, iron, vitamins and essential fatty acids, appropriate heat are also advised at the same time. In order to check the compliance of the subject, the drug package and aluminum cardboard are asked to return to researchers at follow-up every two weeks, patients should be emphasized that they return all the drug packages, including the pharmaceutical packages that are not taken and run out of, which will help researchers to analyze the patient medication correctly. The number of tablets is to count and determine how much of the remaining drugs and the drugs the patients have taken. During the period of study, patients who participate in this study are not allowed to use other drugs that may affect the effect of iron supplementation. In special circumstances, the patient will be excluded because of using other drugs that affect the absorption of iron or vitamin C. The patients will receive blood routine examination at follow-up every two weeks, the results of examination,the reason and number of termination and loss, the incidence of adverse events in patients, such as, nausea, vomiting, abdominal pain, diarrhea and constipation are all recorded. Finally, we analyze the data to determine the effect and safety of vitamin C for iron supplementation. In this study, we hypothesis that vitamin C can increase the absorption of iron and accelerates the recovery of anemia, it also increases the incidence of gastrointestinal adverse events because of increased iron absorption at the same time.