What is haemoglobin?
Haemoglobin is an iron-containing protein inside your red blood cells that carries oxygen from your lungs to every tissue in your body, and helps transport carbon dioxide back to the lungs for you to breathe out. Because oxygen powers virtually every cell in your body, haemoglobin has a direct impact on energy, endurance, brain function, recovery and overall wellbeing. It is one of the most commonly tested markers as part of a full blood count in Australia.
Results are reported in grams per litre (g/L) in Australia, and reference ranges differ significantly between men and women, and across life stages. Haemoglobin is one of the most useful markers for identifying anaemia, dehydration and some cardiovascular or respiratory conditions early. You can read more in our complete guide to the haemoglobin blood test.
Why does haemoglobin matter for long-term health and wellbeing?
Haemoglobin determines how efficiently oxygen is delivered to your muscles, brain and organs, which supports everything from daily energy and mental clarity to sleep quality, exercise performance and recovery. When haemoglobin is too low, oxygen delivery is impaired, and this can drive fatigue, breathlessness, brain fog, poor exercise tolerance and hair changes. When haemoglobin is too high, blood can become thicker, increasing strain on the heart and raising the risk of blood clots.
Research shows a U-shaped relationship between haemoglobin and long-term mortality, meaning both very low and very high levels are associated with higher risk. In Australia, about 22 percent of women have depleted iron stores, and around 15 percent of premenopausal women have anaemia. Tracking haemoglobin gives an early, actionable window into your oxygen-carrying capacity, and it is one of the markers Vively looks at as part of its baseline health testing.
What is an ideal haemoglobin level?
In Australia, typical reference ranges are around 130 to 180 g/L for adult men and 115 to 165 g/L for non-pregnant adult women, though ranges vary slightly between labs. Pregnancy has different thresholds, with haemoglobin naturally lower due to increased blood volume, and lower cut-offs are used to diagnose pregnancy anaemia. Interpretation depends on age, sex, life stage, altitude, smoking status, medications and other markers.
There is no single ideal number. A haemoglobin comfortably within the reference range, alongside healthy ferritin, B12, folate, kidney function and inflammation markers, is generally reassuring. A trend over time is often more informative than a single reading, especially in menstruating women, older adults, endurance athletes or people with chronic conditions.
What influences haemoglobin levels?
Nutrition plays a major role, particularly iron, vitamin B12, folate, protein and vitamin C, all of which are needed to make healthy red blood cells. Sex, age, menstrual cycle, pregnancy, breastfeeding, altitude and smoking status also influence haemoglobin, with people living at higher altitudes and smokers often sitting at the higher end of the reference range. Kidney health matters too, since the kidneys produce erythropoietin (EPO), the hormone that signals the bone marrow to make red blood cells.
Chronic illness, inflammation, infection, blood loss (including heavy periods, gastrointestinal bleeding and blood donation), hormonal issues, autoimmune disease, thyroid dysfunction, coeliac disease and inflammatory bowel disease can all shift haemoglobin. Medications and treatments including chemotherapy, some immunosuppressants, testosterone therapy, some diuretics and erythropoiesis-stimulating agents can also affect results. Endurance training, dehydration and recent blood transfusion are other common influences.
What are the symptoms of low haemoglobin?
Low haemoglobin (anaemia) means less oxygen is reaching your tissues, which can cause fatigue that does not improve with rest, weakness, breathlessness on exertion, dizziness or light-headedness, pale skin, palpitations, headaches, cold hands and feet, and reduced exercise tolerance. Some people also notice brain fog, poor concentration, low mood, restless legs, hair shedding, brittle nails, mouth ulcers or cravings for ice (called pica).
Symptoms often develop gradually and can be mistaken for stress, poor sleep or ageing, which is why testing is far more reliable than guessing. Iron deficiency without anaemia (where haemoglobin is still in range but iron stores are depleted) can also cause many of the same symptoms, as covered in our article on iron deficiency signs and how to get tested.
What causes low haemoglobin?
Iron deficiency is the most common cause of low haemoglobin in Australia, particularly in menstruating women, pregnant women, vegetarians and vegans, growing children and endurance athletes. Other nutritional causes include vitamin B12 deficiency, folate deficiency and insufficient protein intake, all of which are essential for making healthy red blood cells. Chronic blood loss from heavy periods, gastrointestinal bleeding, ulcers or frequent blood donation is another major cause.
Chronic diseases and inflammation can lower haemoglobin through what is called anaemia of chronic disease, which can occur with kidney disease, autoimmune conditions, chronic infections, coeliac disease, inflammatory bowel disease and some cancers. Genetic conditions such as thalassaemia and sickle cell disease also affect haemoglobin. Some medications, chemotherapy and radiation, bone marrow disorders and haemolysis (accelerated red blood cell destruction) are less common but important causes.
What are the symptoms of high haemoglobin?
Mildly raised haemoglobin often has no obvious symptoms and may be discovered on routine testing. When symptoms do occur, they can include headaches, dizziness, blurred vision, fatigue, itching (particularly after a hot shower), flushed or ruddy skin, high blood pressure, sweating and, in more significant elevations, joint pain, abdominal discomfort or symptoms of blood clots such as leg swelling, chest pain or breathlessness.
Because these signs overlap with many other conditions, high haemoglobin is best interpreted alongside your medical history, medications, smoking status, altitude and other blood markers. Any significantly elevated haemoglobin should be reviewed by your GP to identify the underlying cause.
What causes high haemoglobin?
Dehydration is a common and reversible cause of falsely elevated haemoglobin, since less fluid in the blood concentrates the red blood cells. Chronic hypoxia (low oxygen) from smoking, chronic obstructive pulmonary disease (COPD), obstructive sleep apnoea, congenital heart disease and living at high altitude is another common driver, as the body increases red blood cell production to compensate. Testosterone therapy and anabolic steroids can also raise haemoglobin significantly.
Less common but important causes include polycythaemia vera (a bone marrow disorder), kidney tumours or cysts that produce excess erythropoietin, some other cancers and use of erythropoiesis-stimulating agents. In these cases, additional tests such as EPO levels, JAK2 gene testing and imaging may be needed. Any persistently high haemoglobin warrants medical review.
What does it mean if haemoglobin is outside the optimal range?
A low haemoglobin suggests reduced oxygen-carrying capacity and points to conditions such as iron deficiency, B12 or folate deficiency, chronic disease, blood loss or a bone marrow problem. It does not diagnose any single condition on its own, but it is a signal worth investigating, particularly if it is significantly low or accompanied by symptoms such as fatigue, breathlessness, palpitations or reduced exercise tolerance.
A high haemoglobin can reflect dehydration, chronic lung disease, smoking, altitude, testosterone use or an underlying bone marrow, kidney or heart condition. Both very low and very high haemoglobin are associated with higher long-term risk, so both deserve clinical attention. As with any marker, patterns over time and the context of your other results matter more than a single reading.
Can haemoglobin be normal but something still be wrong?
Yes, a haemoglobin within the reference range does not always rule out an iron or nutritional problem. Iron stores can be depleted for months before haemoglobin actually falls, so ferritin, transferrin saturation and other iron studies often reveal early deficiency that a full blood count misses. This is one of the most common patterns behind unexplained fatigue in menstruating women, athletes and vegetarians.
Haemoglobin can also be misleading in specific situations. It can appear falsely elevated with dehydration, or falsely reassuring in pregnancy when blood volume expansion masks a real reduction in red blood cell mass. Recent blood transfusion, some inherited conditions and unusual assay results can also affect interpretation, which is why haemoglobin is best interpreted alongside iron studies, B12, folate, kidney function and inflammation markers.
What other markers should be checked with haemoglobin?
Haemoglobin is most useful as part of a full blood count, which also measures red blood cell count, haematocrit, mean cell volume (MCV), mean cell haemoglobin (MCH), red cell distribution width (RDW), white blood cells and platelets. MCV in particular helps distinguish types of anaemia: low MCV suggests iron deficiency or thalassaemia, while high MCV points more towards B12 or folate deficiency, alcohol use, liver disease or thyroid issues.
Ferritin, iron, transferrin and transferrin saturation help identify iron deficiency, and B12 and folate help identify other nutritional causes. Kidney function (creatinine, eGFR), thyroid function (TSH), inflammation markers such as hs-CRP and, where relevant, coeliac serology, reticulocyte count and EPO can help clarify the underlying cause. In endurance athletes, checking these markers regularly can help catch depleted stores early, and you can see the full set of markers Vively looks at through our tests page and shop tests page.
How can you improve haemoglobin to a healthier level?
If haemoglobin is low, the right approach depends on the cause, so identifying why it is low is more important than simply chasing a higher number. Nutritional strategies that support healthy haemoglobin include eating iron-rich foods (lean red meat, poultry, fish, legumes, tofu, spinach, pumpkin seeds and fortified cereals), pairing plant iron sources with vitamin C to improve absorption, and including adequate B12 (from animal foods or fortified plant foods), folate and protein. Reducing tea, coffee and calcium intake close to iron-rich meals can also help absorption.
Treating underlying causes such as heavy periods, coeliac disease, gastrointestinal blood loss, thyroid dysfunction or chronic inflammation is often the most important step, and iron supplements or infusions may be recommended by your GP for significant iron deficiency. If haemoglobin is high, addressing dehydration, quitting smoking, managing sleep apnoea, reviewing testosterone therapy or investigating underlying causes with your GP are the main levers. Not every marker can or should be self-optimised, and Vively's how it works page explains how testing, monitoring and dietitian coaching combine to make sustainable change practical.
When does haemoglobin need medical review?
See your GP if your haemoglobin is significantly low or high, if it is trending in an unexpected direction, or if you have symptoms such as ongoing fatigue, breathlessness, palpitations, dizziness, headaches, unexplained bruising or bleeding, unexplained weight loss or reduced exercise tolerance. Any suspected blood loss (such as blood in the stool, black stools or heavy periods) needs clinical assessment. Very low or very high haemoglobin warrants prompt review.
Clinical input is important during pregnancy, when planning pregnancy, when breastfeeding, and in older adults, endurance athletes, vegetarians, vegans, people with chronic conditions such as kidney disease, coeliac disease, inflammatory bowel disease or autoimmune disease, and people on testosterone therapy or other medications known to affect haemoglobin. Haemoglobin should never be self-diagnosed, as it is one piece of a bigger clinical picture your GP or specialist can help you interpret.
How does Vively help you understand haemoglobin?
Haemoglobin is one of the blood markers included in the Vively Baseline Health Check, alongside a full blood count, ferritin, iron studies, B12, folate, kidney function, thyroid function, inflammation markers and more than 60 other biomarkers in total. Rather than looking at haemoglobin in isolation, Vively interprets it in context with your other results, symptoms, diet, medications, life stage and menstrual history. This helps identify whether a low haemoglobin is driven by intake, absorption, blood loss or inflammation, and whether a high haemoglobin is more likely from dehydration, lifestyle or an underlying condition.
A registered nurse reviews your results with you one on one, and accredited practising dietitians support the changes that follow. Because your markers are retested over time, you can see how nutrition, supplementation, movement and lifestyle are actually shifting your haemoglobin and broader health profile. Start at the Vively homepage or explore the full range of tests in the Vively shop.
References
- Royal College of Pathologists of Australasia. RCPA Manual: Haemoglobin. https://www.rcpa.edu.au/Manuals/RCPA-Manual/Pathology-Tests/H/Haemoglobin
- Healthdirect Australia. Full blood count (FBC). https://www.healthdirect.gov.au/full-blood-count-fbc
- Better Health Channel, Victorian Department of Health. Anaemia. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/anaemia
- Royal Australian College of General Practitioners. Guidelines for preventive activities in general practice (Red Book). https://www.racgp.org.au/clinical-resources/clinical-guidelines/key-racgp-guidelines/view-all-racgp-guidelines/red-book
- World Health Organization. Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity. https://www.who.int/publications/i/item/WHO-NMH-NHD-MNM-11.1
- Australian Institute of Health and Welfare. Australia's health. https://www.aihw.gov.au/reports-data/australias-health
- Lifeblood (Australian Red Cross). Iron and blood donation. https://www.lifeblood.com.au/
- Pasricha SR, Tye-Din J, Muckenthaler MU, Swinkels DW. Iron deficiency. The Lancet. 2021;397(10270):233 to 248.
- Camaschella C. Iron-deficiency anemia. New England Journal of Medicine. 2015;372(19):1832 to 1843.
- Tefferi A, Barbui T. Polycythemia vera and essential thrombocythemia: 2019 update on diagnosis, risk stratification and management. American Journal of Hematology. 2019;94(1):133 to 143.
- National Institutes of Health, MedlinePlus. Hemoglobin test. https://medlineplus.gov/lab-tests/hemoglobin-test/
- Cleveland Clinic. Hemoglobin test. https://my.clevelandclinic.org/health/diagnostics/17790-hemoglobin-test
- Mayo Clinic. Hemoglobin test. https://www.mayoclinic.org/tests-procedures/hemoglobin-test/about/pac-20385075
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