To understand your fatigue or other symptoms better, your doctor may ask you to have a blood test.
What does this mean for you?
A blood test is a simple procedure that involves a small sample of blood being taken from you, usually from your arm. Your doctor will ask a laboratory to test this sample of blood and tell them what to look for. Among other things, your doctor may be interested in answering two important questions related to your symptoms:
- Are you anaemic?
- Are you iron deficient?
How might your blood tests results help answer these questions?
Anaemia occurs when there are fewer healthy red blood cells in your blood or you have haemoglobin below normal levels.1 Haemoglobin carries oxygen in the blood from the lungs to the rest of the body. Your doctor can check whether or not you are anaemic by performing a Complete Blood Count. This helps your doctor to find out the number of red blood cells and amount of haemoglobin in your blood.2
The Complete Blood Count will also tell your doctor what proportion of your blood is made up by red blood cells (known as haematocrit). If you are anaemic, your red blood cell count, amount of haemoglobin and haematocrit will be low. The average red blood cell size (Mean Corpuscular Volume, MCV) and the average amount of haemoglobin within a red blood cell (Mean Corpuscular Haemoglobin, MCH) is also calculated from the sample.2
The table below shows the number of red blood cells, amount of haemoglobin and haematocrit level that may be considered ‘low’ by your doctor. These ranges can be different for different groups of people.3
| Blood Test | Men > 15 Years Old | Women NonPregnant > 15 Years Old | Women Pregnant |
|---|---|---|---|
| Hemoglobin (g/dL)3 | < 13 | < 12 | < 11 |
| Hematocrit(L/L)3 | < 0.39 | < 0.36 | < 0.33 |
| Red Blood Cell Count,3,4 | Normal range: 3600 - 5600 per mm3 | Normal range: 4200 - 5800 per mm3 | |
| Mean Corpuscular Volume, MCV4 (Average red blood cell size; fL) | < 80 | ||
| Mean Corpuscular Haemoglobin, MCH4 (Average amount of haemoglobin within a red blood cell; pg) | < 27 | ||
*THE GUIDELINE VALUES AND THE UNITS PROVIDED IN THIS TABLE ARE FOR YOUR REFERENCE ONLY. IT IS POSSIBLE THAT YOUR DOCTOR USES DIFFERENT GUIDELINE VALUES OR UNITS. TALK TO YOUR DOCTOR ABOUT WHAT YOUR RESULTS MEAN.
Your doctor may also test your blood for iron deficiency either as part of the first blood test, or in a follow-up test. Several different results from your blood test can help a doctor to understand whether or not you are iron deficient. These include:
- TSAT, or serum* transferrin saturation,5 that indicates the amount of iron in your blood that is bound to a substance called transferrin
- Serum* ferritin, which indicates the amount of iron stores you have in your body6
- Serum* iron, the total amount of iron present in the serum of your blood6
- TIBC, or Total Iron-Binding Capacity, which is a measure of the amount of iron your blood can carry7
*WHERE MENTIONED, SERUM IS THE FLUID PART OF THE BLOOD ONCE THE BLOOD CELLS HAVE BEEN REMOVED.
The table below shows the values that may be used by your doctor to determine if you are iron deficient.
| Blood Test Result | Guideline Values |
|---|---|
| Serum Ferritin | << 30 µg/L for patients without co-existent inflammatory disease.8 If inflammatory disease is present, values of 100 µg/L may still be consistent with iron deficiency.8 |
| Serum Iron | < 60 µg/dL4 |
| Total iron binding capacity (TIBC) | > 410 µg/dL4 |
| Transferrin saturation (TSAT) | < 20%9 |
*THE GUIDELINE VALUES AND THE UNITS PROVIDED IN THIS TABLE ARE FOR YOUR REFERENCE ONLY AND IT IS POSSIBLE THAT YOUR DOCTOR USES DIFFERENT GUIDELINE VALUES OR UNITS. TALK TO YOUR DOCTOR ABOUT WHAT YOUR RESULTS MEAN.
Depending on the results of your blood tests, your doctor may diagnose you as being iron deficient or as having iron deficiency anaemia. They may also discuss treatment options with you.
- Wood MM, Elwood PC. Symptoms of iron deficiency anaemia: A community survey. Br J Prev Soc Med. 1966;20:117-121.
- Dean L. 1. Blood and the cells it contains. Blood Groups Red Cell Antigens. 2005:1-6.
- World Health Organization. Iron deficiency anaemia. Assessment, prevention and control: A guide for programme managers.; 2001:1-114.
- Khusun H, Yip R, Schultink W, Dillon DHS. World Health Organization Hemoglobin Cut-Off Points for the Detection of Anemia Are Valid for an Indonesian Population. J Nutr. 1999;129:1669-1674.
- Seid MH, Derman RJ, Baker JB, Banach W, Goldberg C, Rogers R. Ferric carboxymaltose injection in the treatment of postpartum iron deficiency anemia: a randomized controlled clinical trial. Am J Obstet Gynecol. 2008;199(4):435.e1-7. doi:10.1016/j.ajog.2008.07.046.
- Suominen P, Punnonen K, Rajamäki a, Irjala K. Serum transferrin receptor and transferrin receptor-ferritin index identify healthy subjects with subclinical iron deficits. Blood. 1998;92(8):2934-9.
- Yip R, Parvanta I, Cogswell M, et al. Recommendations to prevent and control iron deficiency in the United States. Morb Mortal Wkly Rep. 1998;47(RR-3):1-29.
- Camaschella (2019). Iron metabolism and its disorders Iron deficiency. Blood, 133,1.
- Fishbane S, Pollack S, Feldman HI, Joffe MM. Iron indices in chronic kidney disease in the National Health and Nutritional Examination Survey 1988-2004. Clin J Am Soc Nephrol. 2009;4(1):57-61. doi:10.2215/CJN.01670408.