The Efficacy and Safety of Vitamin C for Iron Supplementation in Adult Patients With Iron Deficiency Anemia



It’s not certain if vitamin C regularly used along in conjunction with iron supplements taken orally is vital for people suffering from anemia caused by iron deficiencies (IDA).

The aim

 to compare the efficacy and dangers of taking oral iron supplements and vitamin C, or oral iron supplements on their own for patients suffering from IDA.

Design Setup, Participants, and Setting 

The single-center, open-label study of equivalence was held beginning on January 1st, 2016 until December 30, 2017 in Huashan Hospital, Fudan University. Adult patients who had been diagnosed with IDA were recruited. Participants were assigned randomly (1:1) to either the oral iron supplements with vitamin C group, or to the only oral iron supplement group. Data analysis was carried out between March and December of 2018.


Patients were randomly allocated to receive a 100 mg oral iron tablet with 200 mg vitamin C or a 100 mg iron tablet by itself every 8 hours for three months.

Major Outcomes and measures 

The main outcome was the alteration in hemoglobin levels between baseline to two weeks of treatment. an equivalence margin of one g/dL of hemoglobin was selected to show similar effectiveness. Other outcomes included the increase in the percentage of reticulocytes after two weeks of therapy, the rise in hemoglobin levels after 4 weeks of therapy, the rise in ferritin levels in the serum following 8 weeks of treatment and adverse outcomes.


In the 440 randomized patients (220 each from an oral supplement with iron with vitamin C group, and the iron-only group, 426 women [96.8 percent]; median [SD] age 38.3 [11.7 years) All were evaluated as a primary outcome and 432 (98.2 percent) completed the study. From baseline to 2 weeks of follow-up period, the mean (SD) changes in hemoglobin levels of hemoglobin was 2.00 (1.08) grams/dL in the iron supplements taken with oral vitamin C group, and 1.84 (0.97) mg/dL in the group that only took oral iron supplements (between-group variation, 0.16 g/dL; 95 percent C.I, -0.03 to 0.35 g/dL) which is in line with the requirements for equivalent results. The average (SD) increase in ferritin levels between baseline and 8-week follow-up is 35.75 (11.52) milliliters for the vitamin C and iron group, as well as 34.48 (9.50) milliliters within the Iron-only category (between-group variation, 1.27 ng/mL; 95 percent C.I, -0.70 to 3.24 ng/mL; P = .21). There was no significant difference between the two groups with regard to the frequency in adverse event (46 [20.9 percentand 45 [20.5 percent and a difference of 0.4 percent (95% CI: -6.7 percentage to 8.5 percentage; P = .82). There was no patient who had to withdraw due to adverse circumstances.

Conclusions and their relevance 

In patients suffering from IDA oral iron supplements were comparable to oral iron supplements and vitamin C in enhancing hemoglobin absorption and recovery. The findings suggest that on demand vitamin C supplements aren’t necessary to supplement oral iron supplements for those suffering from IDA.


The condition of iron deficiency (IDA) is linked to an increase in erythropoiesis, caused by a deficiency in the body’s total iron.  Iron deficiency is the main cause of anemia across the globe. As per the World Health Organization guideline,  IDA impacts 30 percent of the world’s population suggesting that it’s an issue that needs to be addressed.

Iron deficiency can be classified into three phases that are prelatent iron deficiency the latent deficiency of iron (also known as iron-deficient erythropoiesis) as well as the iron deficiency (IDA). At the beginning stage, an intake of iron lower than the amount required causes the gradual depletion of the iron storage mostly in the muscle and liver cells. Patients in this stage typically don’t exhibit any symptoms however, the identification of deficiency in iron occurs when the levels of ferritin in the serum (the ferritin that stores iron) fall to less than 20ng/mL (to translate to micrograms of iron per liter multiply it by 1.0). The depletion of iron storage continues to lead to the next level of the iron deficiency iron-deficient erythropoiesis. In this stage, iron deficiencies develop and begin to influence the erythropoiesis. In spite of an increase in transferrin levels the level of iron in the blood decreases with increasing the saturation of transferrin. Erythropoiesis impairment is evident when iron content of the blood drops by less than 50.3 mg/dL (to convert it to micromoles/liter multiply the number by 0.179) and the transferrin saturation is below 16 percent. 4 Hemoglobin level remains in the normal range up to the stage of IDA stage. The levels of iron storage decrease to the point where they no longer can aid in hemoglobin production or produce sufficient the red blood cells (RBCs). A deficiency in iron can affect RBC production of hemoglobin and synthesis and can cause anemia. 5

In the phase of prelatent iron deficiency the iron-rich diet is able to be used to treat the majority of cases. However, those suffering from IDA need iron supplementation to replenish their storage iron, improve hemopoiesis, treat anemia and alleviate the symptoms. 3

Iron supplements taken orally are the main method of restoring the levels of iron in patients suffering from IDA. Many nonheme iron supplements are available and ferrous sulfate as well as ferric succinate are the most popular. Vitamin C is the only food ingredient aside from animal tissues which has been proven to increase the absorption of iron. 6 6 – 6 – Absorption of iron is mostly in the duodenum and the upper jejunum, in which ferrous iron is transported into mucosal small intestine epithelial cells. When consumed by mouth, iron transformed into an Fe 3+ state, which is different from its initial form. The iron needs an acidic stomach environment in order to dissolve properly to be absorbed. Vitamin C could create an acidic environment inside the stomach and prevent the oxidation of ferrous iron into ferric iron. 10 However the study found that, in 12 people receiving iron in the course of a standard or supplemented with vitamin C, 8 the effects of vitamin C in promoting iron absorption in a full-time diet was less evident than when consuming one meal. The beneficial effects of vitamin C when combined in conjunction with food on iron status is not significant. 8 , 11 Thus the question of whether vitamin C can provide other benefits, like increasing the effectiveness of iron tablets, and consequently, speeding up the recovery process for anemia is not fully comprehended. The question of whether iron tablets containing vitamin C supplements are recommended is a debate.

We know that until this point, there was not any randomized clinical trials (RCT) to test whether vitamins C are required for patients suffering from IDA who take tablets of iron. Thus, it is essential to conduct a thorough RCT to evaluate the efficacy and safety of taking oral iron supplements by themselves or with vitamin C for patients suffering from IDA. We developed a single-center Equivalence RCT to assess whether oral iron supplements were equivalent to oral iron supplements with vitamin C, and to test whether vitamin C, which is commonly used in conjunction in conjunction with iron supplements could improve the absorption of iron.


Study Design

The two-year, open-label single-center RCT was carried out in Huashan Hospital, Fudan University, Shanghai, China. The patients gave written informed consent prior to the beginning in the research. The review board for the institution of Huashan Hospital, Fudan University has approved the research. This study adheres to guidelines of the Consolidated Standards of Reporting Trials ( CONSORT) guidelines for reporting.

Randomization of participants in 1:1 ratio was conducted with Stata statistical software, version 11.0 (StataCorp) through the use of a randomization process ( Figure 1). A sequentially-numbered sealed, opaque envelopes made sure that randomization was not visible. The serial numbers on the exterior of envelopes was in line with the visits of the patients’ numbers. Following baseline measurements the doctor handed over the sealed envelope with the patient’s eligible consulting number. The patient then took the envelope and opened it, that contained information about the randomization group assigned to them.

The group receiving the intervention received an oral iron 100-mg tablet (ferrous succinate 100 mg/tablet) along with 200 milligrams of vitamin C (vitamin C 100 mg per tablet) each 8-hour period while the control group was given a 100 mg iron tablet (ferrous succinate 100 mg/tablet) every 8 hours. The patients all took the tablets with warm water for about half an hour following a meal. To determine compliance, we determined the amount of tablets containing vitamin C and iron given to the participants. The entire trial protocol is available in Supplement 1..

Study Population

We examined patients who had been discovered to have IDA who have not received any iron supplementation therapy at Huashan Hospital, Fudan University between the 1st of January, 2016 until December 30th in 2017. Certain of these patients were discovered to be anemic during the routine examination. The majority of patients complained of symptoms such as dizziness or palpitations. Nurses first checked the patient for dizziness and palpitations. If the patients were discovered to be anemic the nurse would suggest the patients go to the clinic for anemia for exam and treatment. Our team then screened the patients for admission.

The criteria for inclusion were 18 or over and voluntarily signing the signed informed consent forms, as well as satisfying the diagnostic requirements for IDA including the hemoglobin level being lower than 13 g/dL or less for males and less than 12 g/dL in females (to convert hemoglobin into grams/liters, divide the number by 10.0) or a MCV (MCV) not exceeding 80 millimeters 3. (to change MCV into Femtoliters, multiplied by 1.0) Mean of corpuscular hemoglobin (MCH) less than 27 pg/cell. Mean corpuscular hemoglobin content (MCHC) below 32 g/dL (to convert MCHC into grams/liters, divide the number by 10) and a ferritin level below 14 ng/mL for women, or 30 ng/mL in males, serum iron less than 39 mg/dL in women and 56 mg/dL in men with a transferring saturation of to less than 20% and total iron binding capacity (TIBC) over 428 mg/dL (to convert TIBC into micromoles for a liter of water, multiplied the number by 0.179). The exclusion criteria included bleeding that was severe and unreparable caused by stomachache or intestinal ulcers, any inflammation or gastrointestinal tumors that have been identified.

Study Monitor

They were monitored for 3 months, and then analyzed by the complete blood count every two weeks for a period of 2 months. the iron metabolism was evaluated in week eight. The primary outcome was increase in hemoglobin levels from baseline to the two-week follow-up. The secondary outcomes were the change in percent of reticulocytes following 2 weeks of therapy, the rise in hemoglobin levels after 4 weeks of treatment an increase in ferritin levels in the serum after the 8-week treatment and the occurrence of adverse incidents. The exploratory outcomes were MCV, MCH, and MCHC levels every two weeks at any time and the iron concentration in serum, the transfer of saturation and TIBC after 8 weeks. In the Department of Laboratory Medicine in Huashan Hospital, Fudan University was responsible for the measurement and biochemical analysis.

Statistical Analysis

The calculation of sample size was done to determine the hemoglobin levels from baseline utilizing an equivalence model; with the limit of 1 g/dL as the mean difference, and a significance threshold of .05 A total number of 392 participants (assuming there was no difference between groups) and a mean measurement of 1.5 g/dL and an acceptable error of 0.5 grams/dL as well as an allocated ratio of 1:1, this would translate to 90% power. If we consider the dropout rate of 10%, it was estimated that 440 people all in all were included for the research.

The results with regular distributions have been confirmed with an examination of normal distributions and presented as means (SD) results. Comparative analysis of ages, baseline of the complete blood count, as well as the iron metabolic parameters among two groups was conducted using the test of t test. Comparative sexes and frequency of adverse reactions between the two groups was basing on a two-sided Pearson KH 2. test. The 95% CIs of the differences in the changes in hemoglobin levels between two groups were calculated at each time point and the equivalence rate was determined by using the predetermined margins of equivalent (+-1 grams/dL). The efficacy factors were evaluated using an intention-to-treat approach. If patients opted out the study, missing data were attributed using the most recent observation carried forward. To evaluate adverse incidents, patients who had received at least one dose of the study drug were enrolled in the safety group. The threshold for statistically significant event was established at P .05. P less than .05. The tests were all conducted with Stata stats software, Version 11.0 (StataCorp) between March through December of 2018. The complete statistical analysis program can be found in Supplement 2..



Of the 530 patients screened for the possibility of eligibility, 90 were rejected. The remaining 444 participants (mean *SD 38.3 [11.7 years) were randomly selected. All patients were followed up until 5 patients from the vitamin C and iron group and 4 in the group with iron only dropped out after two weeks. The compliance rate was 98.2 percent (432 people). The figure 1 illustrates how participants moved the trial.

Of the 426 patients in the study of whom 426 (96.8 percent) were women who had a median aged that was 38.1 years (range between 18 and 90 years). The most frequent reason for IDA among women was menorrhagia caused by endometriosis or uterine fibroids which was reported at 389 patients (91.3 percent) in the study. Other causes included hemorrhoidal hemorrhage (9 cases [2.1 %]), vegetarian diet (7 patients [1.6 %]), fecal occult blood positive due to bleeding in the gastrointestinal tract (4 cases [0.9 %]), repeated hematuria (1 patients [0.2 %]), and unknown (16 patients [3.8 %]). 14 of the patients (3.2 percent) were men, with an average time of 61.4 years (range from 24 to 80 years) and had a variety of causes for IDA that included hemorrhoidal bleeding (5 cases [35.7 %]), bleeding ulcer (4 patients [28.6 %]), gastric cancer after surgery (3 patients [21.4 %]), intestinal inflammation (1 patient [7.1 %]), and colon cancer following colon cancer after surgery (1 patients [7.1 %]). There there were no significant differences between the two groups with respect to the baseline features ( Table 1).


Primary Outcome: Change in Hemoglobin Level

From baseline to follow-up of 2 weeks The average (SD) changes in hemoglobin levels of hemoglobin was 2.00 (1.08) mg/dL in the vitamin C group with iron as well as 1.84 (0.97) mg/dL in the group with iron only (mean difference between groups: 0.16 g/dL 95% CI, -0.03 to 0.35 g/dL). The primary outcome was that the hemoglobin levels change between baseline and follow-up of 2 weeks was within the equivalence limit one gram/dL ( Figure 2) Therefore there was no statistically significant difference in the hemoglobin level rise between the two groups. Also there was no statistically substantial difference between the increase in hemoglobin levels at weeks 4 6 and 8 ( Table 2).

Secondary Outcomes: Changes in RBC Parameters

The median (interquartile interval) changes in the reticulocyte count after a two-week follow-up was 1.03 percent (0.74%-1.20 percent) within the vitamin-C and iron group, and 1.04 percent (0.50%-1.20 percent) within the only iron group (between-group differences of 0.11 percent 95% CI, 0.10 percent to 0.32 percent) This difference was not statistically significant. Similar results were observed at week 4, 6 and 8 with not significant distinctions between two types ( Table 2).

The MCV levels and the MCH level rose little (all 95 percent CIs were in the positive range) within the group of vitamin C and iron at every follow-up point ( Table 2). The rise in MCHC levels was greater for those in the group with vitamin C with iron after 6 weeks in duration, with the mean (SD) variations within MCHC that were 3.10 (1.33) grams/dL for the Vitamin C with iron, and 2.82 (1.41) mg/dL in an iron-only population (between-group variation of 0.28 g/dL 95% CI, 0.02-0.53 mg/dL). Changes in RBC distribution in width coefficient of variation demonstrated no significant differences between the two groups at any time points of follow-up ( Table 2).

Iron Metabolism Parameters

Also, no differences were noticed between the two groups regarding the changes in ferritin levels from baseline to 8 weeks of follow-up. The median (SD) variation is 35.75 (11.52) milliliters for the vitamin C and iron group, and 34.48 (9.50) mg/mL in the group with iron only (mean of the two groups was 1.27 ng/mL 95% CI -0.70 from 3.24 mg/mL, the P > .21). The changes in the blood iron levels, saturation for transferring and TIBC were similar between the two groupings ( Table 2).

Adverse Events

The treatment was similarly tolerated for an 8-week period of post-treatment follow-up. The most common adverse reactions included stomach upset, nausea and acid reflux ( Table 3). The percentage of patients who experienced adverse events was similar between the two groups, in the vitamin C plus iron group, 46 (20.9 percent) within the vitamin-C and iron group, and 45 (20.5 percent) for the only iron category after two months of following-up (difference, 0.4%; 95 percent CCI, -6.7% to 8.5 percentage; P = .82). After two weeks of treatment, the patients who had adverse events reported feeling better, and another 23 patients were able endure those adverse reactions. None of the patients decided to withdraw due to adverse incidents ( Table 3).


The results show that oral iron supplements on their own can provide hemoglobin levels and the ability to recover iron storage comparable to oral iron supplements containing vitamin C for patients suffering from IDA. According to our research the present RCT was the very first study to examine the safety and efficacy in vitamin C supplementation with oral iron for patients suffering from IDA.

Oral iron can be a cheap and efficient method of restoring iron balance for patients suffering from IDA. Vitamin C can be the sole food ingredient aside from animal tissues that has been proven to enhance in the absorption and utilization of nonheme Iron in human beings. 9 

According to some doctors think that vitamin C may enhance the effectiveness for oral iron as well as accelerate the treatment of anemia suggest using vitamin C supplements in conjunction with iron tablets taken orally. However, the total dosage of vitamin C was not related to iron absorption when consuming an entire diet. The improvement of iron levels was not evident, which was in accordance with our results that show that iron supplements alone offers the same effectiveness of oral iron supplemented with vitamin C. The hemoglobin levels changed levels were comparable between the two groups at weeks 2, 4 6 and 8. The variation in hemoglobin levels is within an equivalence threshold of +1 g/dL. This is the minimum threshold for clinically significant changes as suggested by hematologists. The changes in MCV between baseline and any time points were higher when compared to the vitamin C and iron group. MCV measures the RBCs’ mean size and patients suffering from IDA generally have lower values than normal. MCV is a measure of the size of RBCs. RBC variables MCH, MCV and the MCHC have greater sensitivity and are useful in assessing the effect of the treatment.  

However, the objective of the treatment was to restore hemoglobin concentrations and replenishing iron stores neither was sensitive to treatment. Iron metabolism parameters like serum ferritin levels, serum iron, the saturation of iron as well as TIBC in week eight were similar between the two groups. Additionally, adverse events were comparable between the two groups.

These findings challenge the suggestion to supplement vitamin C supplements along with iron orally to increase the effectiveness of the supplement and speed recuperation from anemia. Iron is absorbed as ferrous salt (Fe ++) in a moderately acidic medium. Theoretically vitamin C can be beneficial in absorption. But, based on the findings of this RCT vitamin C could not be as beneficial as previously reported and anticipated.


The study is not without its limitations. First 426 of the patients were females while 19 men this was a significant unbalance. In addition, the duration of follow-up was not sufficient. We discovered that patients with iron deficiency anemia was prone to relapse in cases where the causes, like iron-absorption issues and bleeding, weren’t examined and treated. A few patients returned to our clinic around one year after the trial had ended due to the relapse. The exact date when iron deficiency resurfaced and whether the rate of relapses was similar between both groups was not known. Future research should prolong the period of observation to gain more precise and reliable results.


The results of this equivalence RCT prove that, in patients suffering from IDA taking oral iron on its own was comparable to supplementing oral iron with vitamin C to improve hemoglobin levels and stores of iron. Our findings indicate that vitamin C isn’t necessary for people suffering from IDA.


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