What is Low Red Cell Distribution Width in Blood (RDW) & How To Intrepret It

Introduction

Understanding blood test results is essential for getting the right care and maintaining good health. Red cell distribution width (RDW) is an important aspect that can provide clues about your overall well-being. 

In this article, you will learn about what RDW is, why it is measured, how to interpret your RDW results, and the potential influence of these results on your health. Together with other blood test indicators, RDW may help you and your healthcare provider come up with a comprehensive management plan tailored to your specific health needs. 

Red Cell Distribution Width (RDW) Test

RDW helps in checking the state of your red blood cells. 

What Is RDW? 

Red cell distribution width (RDW) is a measure of the difference in size and volume of your red blood cells¹². It’s part of a complete blood count (CBC). This routine blood test gives us a picture of your overall health. RDW is key to detecting possible blood disorders and tracking existing illnesses.  

Why Is The RDW Test done? 

RDW tests aim to help detect and keep track of certain health issues. Working with other blood test checks, RDW helps in finding out if you have the following¹².  

• Anaemia^3,4
• Deficiency of iron, vitamin B12, or folate 
• Thalassaemia 
• Ongoing liver or kidney disease 
• Diabetes mellitus 
• Heart failure 

How Do You Prepare for the Test? 

Getting ready for an RDW test is simple. No need to fast or make any other special changes. Just go by your healthcare provider’s orders before the test.  

Interpreting RDW Results

Understanding RDW Ranges 

RDW values are given as a percent. They tell us about the sizes of your red blood cells¹. For adults, the normal range is between 11.5% and 15.4%. This can change based on the laboratory and instrument used. RDW ranges come in three types: normal, high, and low¹². 

• Normal range: This says all your red blood cells are the same size and shape. 
• High range: High RDW means bigger size changes. It points to possible health problems, like anaemia³ or a lack of nutrients. 
• Low range: A low RDW is often seen as normal. A low RDW doesn’t mean any blood problems. 

Factors Affecting RDW 

Many things may affect RDW levels.  

• Lack of water in the body⁵. 
• Lifestyle habits, like diet, physical activities, and sleep⁶. 
• Some drugs, like blood thinners or antiviral drugs. 

Research has demonstrated that RDW is linked to a bad outcome in individuals with multiple myeloma and lung cancer¹³. Additionally, it may predict cancer in those who have lost weight inadvertently⁸.

Dr. Siddharth Gupta, BAMS, MD (Ayu)

Low Red Cell Distribution Width

Causes of low RDW

Low RDW mainly shows that your red blood cells are the same in size and shape.  Some factors might fake a low RDW. These are as follows. 

Potential Risks and Complications:

Low RDW doesn’t directly cause trouble. But conditions tied to low RDW might impact your health.  

If your blood test reveals low red cell distribution width, your healthcare provider will check your signs and symptoms and may look at other blood test parameters to assess the reason behind this. 

Other Important Blood Test Indicators

Besides RDW, other blood tests are vital in gauging your health. 

• Mean Corpuscular Volume (MCV): Mean corpuscular volume (MCV) is another key blood test. It finds out the mean size of your red blood cells. It’s often part of a CBC. MCV results can give helpful information about the kind of anaemia you might have or if you’re at risk of lacking certain nutrients. The bond between RDW and MCV can shed light on your health state⁹. 
• Haemoglobin and Hematocrit Levels: Haemoglobin and hematocrit levels also matter a lot in blood tests. Haemoglobin is a protein in red blood cells that carries oxygen. Hematocrit tells us the red blood cells’ volume percentage in the blood¹⁰. 

In reading RDW results, thinking about haemoglobin and hematocrit levels together is key. This combination gives a full view of your blood health. It helps healthcare providers make smart choices about your health. 

Management of Low RDW

The right care and steps are vital for handling the root cause of low RDW. 

1. Addressing the Underlying Cause 

In managing low RDW, dealing with the root cause is most important. This means making the right tests, knowing the exact issue, and modifying the management plan accordingly. In some cases, your healthcare provider may suggest drugs, supplements, or lifestyle changes. 

2. Dietary and Lifestyle Changes 

Eating a balanced diet rich in iron aids a lot in improving RDW levels¹¹. Having foods high in vitamins, minerals, and key nutrients may help. Moreover, regular exercise and enough water intake may also help improve your blood health. 

3. Monitoring and Follow-Up Tests 

Doing regular blood tests is key to tracking your RDW levels and controlling any ongoing health issues. This ensures your management plan is made to meet your exact requirements. It also allows for needed changes in your health plan. 

Conclusion

Knowing the value of low RDW and using this key information may help you maintain health. By tracking your RDW results and working in sync with your healthcare provider, you may manage your health well. Moreover, fixing the root cause of low RDW and implementing the lifestyle and dietary changes required is vital.  

Frequently Asked Questions (FAQs)

References

1. PubMed. Poikilocytosis [Internet]. [cited 2024 Feb 13]. Available from: https://pubmed.ncbi.nlm.nih.gov/32965812 
2. National Center for Biotechnology Information (NCBI). The role of red blood cell distribution width (RDW) in cardiovascular risk assessment: useful or hype? – PMC [Internet]. [cited 2024 Feb 13]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6861793 
3. National Center for Biotechnology Information (NCBI). Macrocytic Anemia [Internet]. [cited 2024 Feb 13]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459295 
4. PubMed. Baseline Red Blood Cell Distribution Width Correlates with Disease Activity and Therapeutic Outcomes in Patients with Systemic Lupus Erythematosus, Irrespective of Anemia Status [Internet]. [cited 2024 Feb 13]. Available from: https://pubmed.ncbi.nlm.nih.gov/28164513 
5. Kim HK, Kim SH, Ryu JK. Changes in the blood components caused by water intake. Korean Journal of Clinical Laboratory Science. 2017;49(3):227-232. doi:10.15324/kjcls.2017.49.3.227. Available from: https://www.kjcls.org/journal/view.html?doi=10.15324/kjcls.2017.49.3.227
6. PubMed. Sleep duration and sleep disorder with red blood cell distribution width [Internet]. [cited 2024 Feb 13]. Available from: https://pubmed.ncbi.nlm.nih.gov/26018095
7. National Health Service (NHS). Thalassaemia [Internet]. London: NHS; [cited 2026 May 21]. Available from: https://www.nhs.uk/conditions/thalassaemia/
8. Ellingsen TS, Lappegård J, Skjelbakken T, Braekkan SK, Hansen JB. Impact of red cell distribution width on future risk of cancer and all-cause mortality among cancer patients – the Tromsø Study. Haematologica [Internet]. 2015 Oct [cited 2026 May 21];100(10):e387-9. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC4591771/
9. MedlinePlus. MCV (mean corpuscular volume) [Internet]. Bethesda (MD): U.S. National Library of Medicine; [cited 2026 May 21]. Available from: https://medlineplus.gov/lab-tests/mcv-mean-corpuscular-volume/
10. Billett HH. Hemoglobin and hematocrit. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations [Internet]. 3rd ed. Boston: Butterworths; 1990 [cited 2026 May 21]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK259/
11. Prentice AM, Mendoza YA, Pereira D, Cerami C, Wegmüller R, Constable A, et al. Dietary strategies for improving iron status: balancing safety and efficacy. Nutr Rev. 2016 Dec 13;75(1):49–60. doi:10.1093/nutrit/nuw055. PMID: 27974599; PMCID: PMC5155616. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC5155616/
12. National Library of Medicine (US). RDW (red cell distribution width) [Internet]. Bethesda (MD): MedlinePlus; [cited 2026 May 21]. Available from: https://medlineplus.gov/lab-tests/rdw-red-cell-distribution-width/
13. Liu Y, Qu J, Hu C, Zhao W, Zhang Y, Luo Y, et al. Relationship between red cell distribution width and lung cancer: evidence from Mendelian randomization and National Health and Nutrition Examination Survey. Discover Oncology. 2025 May 22;16:867. doi:10.1007/s12672-025-02718-6. PMID: 40405015; PMCID: PMC12098219. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC12098219/

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