European Journal of Cardiovascular Medicine

Glycated hemoglobin (HbA1c) is the preferred criterion for assessing the long-term level of glycemic control in individuals with diabetes mellitus (DM)(1).It provides an indication of the patient's blood sugar levels throughout the past 3 months. HbA1c is commonly employed as a screening tool for diabetes mellitus. Moreover, a HbA1c level of ≥6.5% (48mmol/mol) is advised as the threshold for diagnosing DM(2). HbA1c is a variant of hemoglobin that has a glucose molecule connected to the end of one or both of its HbA beta chains, specifically to the terminal NH2 group of the valine residue. Red blood cells have high permeability to plasma glucose molecules, allowing them to easily pass through. Additionally, hemoglobin in red blood cells is exposed to similar amounts of glucose as seen in the plasma. Consequently, the levels of HbA1c provide a more precise indication of glycemic control during the previous 2 to 3 months, taking into account the lifespan of red blood cells prior to the measurement(3). HbA1c is clinically utilized to assess changes in glycemic control by comparing serial HbA1c values and determining if patients are meeting their HbA1c targets. Additionally, it has recently been recommended for diagnosing type 2 diabetes mellitus (DM). [2]Various factors can influence or disrupt the results of HbA1c measurements, depending on the methodology employed(1).

Historically, some illnesses and pathological conditions, such as anemia and hemoglobinopathies, have been recognized as potential factors that can substantially impact HbA1c results (4). Anemia is a global public health issue that impacts populations globally. The main factor responsible for this is a lack of iron, often known as iron deficiency (ID). Around 33% of anemia patients suffer from iron deficiency, often known as IDA (5). Multiple research have been conducted to investigate the impact of anemia on HbA1c levels. However, the findings of these investigations are inconsistent.[6] Due to the significant impact of HbA1c in diagnosing diabetes mellitus and the widespread occurrence of anemia globally. This study sought to examine the impact of iron deficiency anemia (IDA) on levels of glycated hemoglobin (HbA1c) in patients who do not have diabetes mellitus (DM).

This study was approved by the Institutional Ethics Committee at the SAIMS. This study was conducted between July 2022 to July 2024. The source of data was patients coming to outpatient and inpatient departments at Sri Aurobindo Institute of Medical Sciences and Post Graduate Institute. Diabetes has been defined as HBA1C ≥6.5% the procedures and rationale for the study will be explained to all patients and informed written consent where possible will be taken in their local language. Socio-demographic data and clinical information will be collected on a semi-structured Performa. One hundred (100) participants of the Diabetic Centre of the Medical College Teaching Hospital (34 males and 66 females) were involved all patients diagnosed with iron deficiency anemia will be thoroughly investigated. All the relevant personal and family history will be obtained and thorough clinical examination done. The study participants were of ages above 18 years. Participants Following investigations are planned CBC, serum ferritin, iron profile, RBS, HB1AC. Excluded from the study were patients not giving consent for the study, Chronic diseases, Subjects who are a known case of DIABETIC BY RBS OR HbA1C STATUS, Subjects opposing the use of their data, less than 18 years of age, on iron supplements, on blood transfusion. The participants who were all consented to take part in the study after a thorough explanation of the aim of the study.  Data for each case will be collected and filled in proforma sheet and master chart for consenting patients who meet the inclusion criteria: Blood reports will be directly transcribed from the reports to the proforma.

Table 1 presents a comparative analysis of iron indices between non-anaemic and iron deficiency anaemia groups. The non-anaemic group exhibited a mean serum iron level of 110.37 ± 24.28 mcg/dL, significantly higher than the iron deficiency anaemia group's mean of 58.85 ± 32.97 mcg/dL (T-test = 9.415, P < 0.0000001). Similarly, serum ferritin levels were markedly elevated in the non-anaemic group at 138.34 ± 42.11 ng/mL compared to 56.28 ± 64.26 ng/mL in the anaemic group (T-test = 7.992, P < 0.0000001). Conversely, the total iron-binding capacity (TIBC) was significantly lower in the non-anaemic group, with a mean of 218.04 ± 85.72 mcg/dL, compared to 398.81 ± 83.42 mcg/dL in the iron deficiency anaemia group (T-test = -11.309, P < 0.0000001). All differences were statistically significant, highlighting the distinct variations in iron metabolism between the two groups.

Table 2 compares the mean haemoglobin levels between non-anaemic and iron deficiency anaemia groups. The non-anaemic group had a significantly higher mean haemoglobin level of 13.74 ± 3.09 g/dL, whereas the iron deficiency anaemia group had a mean level of 6.74 ± 3.72 g/dL. The independent student's t-test value of 10.83 (dF = 110) and the P-value of <0.0000001 indicate that this difference is statistically significant, underscoring the substantial disparity in haemoglobin levels between the two groups.

Table 3 illustrates a comparison of mean HbA1c values between iron deficiency anaemia and non-anaemic groups. The mean HbA1c value for the iron deficiency anaemia group was 6.04 ± 0.74%, significantly higher than the 4.91 ± 0.65% observed in the non-anaemic group. The independent student's t-test value of 8.58 (dF = 110) and the P-value of <0.0000001 confirm that this difference is statistically significant, indicating a notable variation in HbA1c levels between the two groups.

Table 4 examines the relationship between the severity of anaemia and HbA1c levels. In the moderate anaemia group (n=25), 20% had HbA1c levels ≤5.5%, 72% had levels between 5.6-6.5%, and 8% had levels between 6.6-7.5%. In the severe anaemia group (n=75), 17.3% had HbA1c levels ≤5.5%, 40% had levels between 5.6-6.5%, and 42.6% had levels between 6.6-7.5%. The Chi-square test value of 6.167 and a P-value of <0.05 indicate that the differences in HbA1c levels across varying severities of anaemia are statistically significant.

Anemia is defined by a decreased lifespan of red blood cells, lower levels of hemoglobin, and the body's attempt to compensate by producing more red blood cells.[7] These factors have a substantial impact on the generation of HbA1c. Iron deficiency has been found to have a separate connection with higher levels of HbA1c, regardless of plasma glucose levels and the severity of anemia.[8]

Out of the total 100 study volunteers, 34% are men and 66% are females.The study conducted by Sinha N et al. [9] found that 68% of the participants were female and 32% were male. These data indicate that iron deficiency anemia is more prevalent in females.

In this study, we included 100 participants with anemia. Among them, 25% had moderate anemia, 75% had severe anemia, and none had mild anemia. A study conducted in Rewa, Rajasthan found that out of 500 cases, 107 (21.4%) had mild anaemia, 315 (63%) had moderate anaemia, and 78 (15.6%) had severe anaemia. In a study conducted in Delhi, India, by Manjhvar SK et al,[10], 76% of the patients were found to have severe anemia, while 24% had moderate anemia. No cases of light anemia were observed.[9]

The predominant manifestations observed in individuals with anemia in the present investigation were pallor (98.2%) and pedal edema (37.5%). According to Manjhvar SK et al,[10], all patients in their study had pallor, with 26.8% having a bare tongue and 27.2% having koilonychia, which were the most often observed indicators. In the study conducted by Sinha N et al,[9], all patients (50/50, 100%) exhibited pallor upon examination. Nail alterations were found in 6 patients, while moderate splenomegaly (<2 cm) was noticed in 12 patients (24%). Additionally, an ejection systolic murmur in the aortic area was observed in 40 patients (80%).

In our present investigation, the proportion of anaemic study subjects was higher among females (64.3%) compared to males (35.7%). The cohort examined by Coban E et al,[11] exhibited a higher number of women (30) compared to men (20) who had iron deficiency anemia (IDA), with an average age of 35.7 +/- 11.9 years. The levels of serum iron, serum ferritin, and TIBC were significantly lower in individuals with iron deficiency anemia compared to the non-anaemic research participants. Sinha N et al,[9] also found that the average initial blood ferritin levels were considerably lower in patients compared to controls (p<0.01).

The average Hemoglobin value was 6.74 ± 3.72 mg/dl in the group with anemia and 13.74 ± 3.09 mg/dl in the group without anemia, indicating a statistically significant difference in the findings. The study conducted in Delhi, India yielded data that demonstrated a statistically significant difference (p<0.01) in hemoglobin levels between anemic patients and healthy controls, confirming that anemic patients had lower hemoglobin levels.[9]

A study conducted in the United States found a direct relationship between Hb concentrations and HbA1c values. Furthermore, it was noted that HbA1c levels exhibited an inclination towards elevation in the presence of iron deficiency. In addition, individuals with iron deficiency anemia (IDA) showed comparable HbA1c levels to those with normal Hb levels and a normal iron status.[12]

Attard et al. [13] conducted a study to assess the impact of iron deficiency and iron deficiency anemia (IDA) on diabetes by examining the levels of HbA1c and fasting blood glucose as diagnostic criteria. The findings indicated that both iron deficiency and IDA led to alterations in HbA1c values, which did not align with the expected clinical condition. The average HbA1c readings were significantly different between the research individuals with iron deficiency anemia and those without anemia. In a study conducted by Rajagopal L et al,[14], similar findings were seen. Non-diabetic individuals with iron deficiency anemia (IDA) had a mean HbA1C % of 6.84±0.07, which was substantially higher (p < 0.05) compared to the non-anaemic group with a mean HbA1C % of 5.12±0.04.

In a study conducted by Sinha N et al,[9], it was shown that the average baseline HbA1c level in anaemic patients (4.6%) was considerably lower than that in the control group (5.5%, P<0.05). Another study conducted at Cukurova University found that the average HbA1c level was considerably lower in the group with IDA (5.4%) compared to the healthy control group (5.9%; p < 0.05).[15]

The proposal suggests that in cases of iron deficiency, the quaternary structure of the hemoglobin molecule is changed, and that glycation of the globin chain happens more easily when there is less iron present. Brooks AP et al [16] and Sluiter et al [17] attempted to offer an explanation for the aforementioned observations. They suggested that the production of glycated hemoglobin is a permanent process, hence, the amount of HbA1 in one red blood cell will steadily rise as the cell ages.

The findings of a comprehensive study conducted across the United States indicate that iron deficiency anemia (IDA) has minimal impact on the overall levels of HbA1c or the prevalence of diabetes in the population. The authors of the study are Ford ES et al.[12] A separate study conducted in India examined 15 individuals without diabetes who had iron deficiency anemia (IDA), as well as 12 control subjects. This study also did not see any significant variation in the average levels of HbA1c. The authors of the study are Rai KB et al.[18]
A study conducted in Denmark demonstrated no significant variations in HbA1c levels between a group of 10 non-diabetic patients with IDA and a group of 10 healthy individuals.[19]

The current study findings shown a notable correlation between the intensity of anemia and the levels of HbA1c in the participants of the study. In a similar manner, Manjhvar SK et al,[10] also observed that non-diabetic patients with iron deficiency anemia (IDA) had significantly elevated levels of glycosylated hemoglobin (HbA1c), indicating that iron deficiency anemia causes an increase in glycosylated hemoglobin values.

Sinha N et al,[9] found a strong association between hemoglobin and HbA1c levels in patients both at the beginning of the study (correlation coefficient=0.593; p<0.01) and after 1 month of treatment (correlation coefficient=0.490; p<0.01). The research conducted by El-Agouza et al,[20] and Coban E et al,[11], demonstrated that individuals with iron deficiency anemia had elevated levels of HbA1c, which considerably decreased following iron treatment. In their study, Rajagopal L et al. [14] also found a direct relationship between iron deficiency anemia (IDA) and increased levels of HbA1C in individuals without diabetes. The level of HbA1C rose in correlation with the degree of anemia. The study conducted by Ford ES et al.[10] found no significant variation in the average HbA1C levels based on the IDA status, both before and after iron treatment.

The average HbA1C level is higher in non-diabetic patients with iron deficiency anemia compared to non-anemic non-diabetic patients. The mean HbA1c level in the control group is 4.91 ± 0.65, but in the case group it is 6.04 ± 0.74. The observed difference is statistically significant (p-value <0.0000001). In iron deficient anemic non-diabetic patients, the HbA1c level is greater compared to non-anaemic non-diabetic patients. In individuals with iron deficiency anemia who do not have diabetes, the amount of HbA1C is higher compared to people without anemia, regardless of their blood sugar level. The severity of anemia is positively correlated with an increase in HbA1c levels. Therefore, it may be inferred that iron deficiency anemia is a distinct factor that influences the HbA1C level in non-diabetic patients. Consequently, it is crucial to interpret this relationship cautiously in all patients with deficiency anemia.

1. Sacks D, Arnold M, Bakris G et al. (2011): Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus. Clin Chem., 57: 1–47.
2. American Diabetes Association (2015): Classification and diagnosis of diabetes. Diabetes Care, 38(1): 8–16.
3. Saudek C, Brick J (2009): The clinical use of hemoglobin A1c. J. Diabetes Sci Technol., 3: 629–634.
4. Sacks D (2011): A1C versus glucose testing: a comparison. Diabetes Care, 34(2): 518-523.
5. World Health Organization (2015): Use of Glycated Hemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus. Abbreviated Report of a WHO Consultation. http://www.who.int/diabetes/en; accessed May 2015.
6. English E, Idris I, Smith G et al. (2015): The effect of anemia and abnormalities of erythrocyte indices on HbA1c analysis: a systematic review. Diabetologia, 58:1409–1421.
7. Gallagher EJ, Bloomgarden ZT, Le Roith D. Review of hemoglobin A1c in the management of diabetes. Journal of Diabetes, 2009, 1:9-17.
8. Kim C, Bullard KM, Herman WH, Beckles GL. Association between iron deficiency and A1C Levels among adults without diabetes in the National Health and Nutrition Examination Survey, 1999–2006. Diabetes Care. 2010;33:780–85. ; Ford ES, Cowie CC, Li C, et al. Iron-deficiency anemia, non- iron-deficiency anemia and HbA1c among adults in the US. J Diabetes. 2011;3:67–73.
9. Sinha N, Mishra TK , Singh T, Gupta N. Effect of iron deficiency anemia on hemoglobin A1c levels. Ann Lab Med. 2012 Jan;32(1):17-22 doi:10.3343/alm.2012.32.1.17. Epub 2011 Dec 20. PMID: 22259774; PMCID: PMC3255499.
10. Manjhvar SK, Singh B, Niranjan AS. To study the effect of iron deficiency anaemia on HbA1c in non-diabetic. J. Evolution Med. Dent. Sci. 2017;6(94):6863-6867, DOI: 10.14260/jemds/2017.
11. Coban E, Ozdogan M, Timuragaoglu A. Effect of iron deficiency anemia on the levels of hemoglobin A1c in nondiabetic patients. Acta Haematol. 2004;112:126–128.]
12. Ford ES, Cowie CC, Li C, Handelsman Y, Bloomgarden ZT. Iron-deficiency anemia, non-iron-deficiency anemia and HbA1c among adults in the US. J Diabetes. 2011;3:67–73
13. Attard SM, Herring AH, Wang H, et al. Implications of iron deficiency/anemia on the classification of diabetes using HbA1c. Nutr Diabetes. 2015;5:e166
14. Rajagopal, Lavanya&Ganapathy, Shivashekar&Arunachalam, Sundaram& Raja, Veena&Ramraj, Balaji. (2017). Does Iron Deficiency Anemia and its Severity Influence HbA1C Level in Non-Diabetics? An Analysis of 150 Cases. Journal of Clinical and Diagnostic Research JCDR.11. EC13-EC15. 10.7860/JCDR/2017/25183.9464.
15. ÇetinkayaAltuntaş, S., Evran, M., Gürkan, E. et al. HbA1c level decreases in iron deficiency anemia. Wien KlinWochenschr 133, 102–106 (2021). https://doi.org/10.1007/s00508-020-01661-6.
16. Brooks AP, Metcalfe J, Day JL, Edwards MS. Iron deficiency and glycosylated haemoglobin A. Lancet. 1980;2:141.
17. Sluiter WJ, van Essen LH, Reitsma WD, Doorenbos H. Glycosylated haemoglobin and iron deficiency. Lancet. 1980;2:531–532.
18. Rai KB, Pattabiraman TN. Glycosylated haemoglobin levels in iron deficiency anaemia. Indian J Med Res. 1986; 83: 234– 6.
19. Gram-Hansen P, Eriksen J, Mourits-Andersen T, Olesen L. Glycosylated haemoglobin (HbA1c) in iron- and vitamin B12 deficiency. J Intern Med. 1990; 227: 133– 6.
20. El-Agouza I, Abu Shohla A, Sirdah M. The effect of iron deficiency anaemia on the levels of haemoglobin subtypes: possible consequences for clinical diagnosis. Clin Lab Haematol. 2002;24:285–289.

1. Sacks D, Arnold M, Bakris G et al. (2011): Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus. Clin Chem., 57: 1–47.
2. American Diabetes Association (2015): Classification and diagnosis of diabetes. Diabetes Care, 38(1): 8–16.
3. Saudek C, Brick J (2009): The clinical use of hemoglobin A1c. J. Diabetes Sci Technol., 3: 629–634.
4. Sacks D (2011): A1C versus glucose testing: a comparison. Diabetes Care, 34(2): 518-523.
5. World Health Organization (2015): Use of Glycated Hemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus. Abbreviated Report of a WHO Consultation. http://www.who.int/diabetes/en; accessed May 2015.
6. English E, Idris I, Smith G et al. (2015): The effect of anemia and abnormalities of erythrocyte indices on HbA1c analysis: a systematic review. Diabetologia, 58:1409–1421.
7. Gallagher EJ, Bloomgarden ZT, Le Roith D. Review of hemoglobin A1c in the management of diabetes. Journal of Diabetes, 2009, 1:9-17.
8. Kim C, Bullard KM, Herman WH, Beckles GL. Association between iron deficiency and A1C Levels among adults without diabetes in the National Health and Nutrition Examination Survey, 1999–2006. Diabetes Care. 2010;33:780–85. ; Ford ES, Cowie CC, Li C, et al. Iron-deficiency anemia, non- iron-deficiency anemia and HbA1c among adults in the US. J Diabetes. 2011;3:67–73.
9. Sinha N, Mishra TK , Singh T, Gupta N. Effect of iron deficiency anemia on hemoglobin A1c levels. Ann Lab Med. 2012 Jan;32(1):17-22 doi:10.3343/alm.2012.32.1.17. Epub 2011 Dec 20. PMID: 22259774; PMCID: PMC3255499.
10. Manjhvar SK, Singh B, Niranjan AS. To study the effect of iron deficiency anaemia on HbA1c in non-diabetic. J. Evolution Med. Dent. Sci. 2017;6(94):6863-6867, DOI: 10.14260/jemds/2017.
11. Coban E, Ozdogan M, Timuragaoglu A. Effect of iron deficiency anemia on the levels of hemoglobin A1c in nondiabetic patients. Acta Haematol. 2004;112:126–128.]
12. Ford ES, Cowie CC, Li C, Handelsman Y, Bloomgarden ZT. Iron-deficiency anemia, non-iron-deficiency anemia and HbA1c among adults in the US. J Diabetes. 2011;3:67–73
13. Attard SM, Herring AH, Wang H, et al. Implications of iron deficiency/anemia on the classification of diabetes using HbA1c. Nutr Diabetes. 2015;5:e166
14. Rajagopal, Lavanya&Ganapathy, Shivashekar&Arunachalam, Sundaram& Raja, Veena&Ramraj, Balaji. (2017). Does Iron Deficiency Anemia and its Severity Influence HbA1C Level in Non-Diabetics? An Analysis of 150 Cases. Journal of Clinical and Diagnostic Research JCDR.11. EC13-EC15. 10.7860/JCDR/2017/25183.9464.
15. ÇetinkayaAltuntaş, S., Evran, M., Gürkan, E. et al. HbA1c level decreases in iron deficiency anemia. Wien KlinWochenschr 133, 102–106 (2021). https://doi.org/10.1007/s00508-020-01661-6.
16. Brooks AP, Metcalfe J, Day JL, Edwards MS. Iron deficiency and glycosylated haemoglobin A. Lancet. 1980;2:141.
17. Sluiter WJ, van Essen LH, Reitsma WD, Doorenbos H. Glycosylated haemoglobin and iron deficiency. Lancet. 1980;2:531–532.
18. Rai KB, Pattabiraman TN. Glycosylated haemoglobin levels in iron deficiency anaemia. Indian J Med Res. 1986; 83: 234– 6.
19. Gram-Hansen P, Eriksen J, Mourits-Andersen T, Olesen L. Glycosylated haemoglobin (HbA1c) in iron- and vitamin B12 deficiency. J Intern Med. 1990; 227: 133– 6.
20. El-Agouza I, Abu Shohla A, Sirdah M. The effect of iron deficiency anaemia on the levels of haemoglobin subtypes: possible consequences for clinical diagnosis. Clin Lab Haematol. 2002;24:285–289.