Haemoglobin

Haemoglobin (Hb) is the iron-containing protein inside your red blood cells that carries oxygen from your lungs to all your tissues. Haemaglobin measures and reflects the oxygen carrying capacity of blood, rather than the total number of red blood cells. When Hb is lower than ideal, your body has less capacity to deliver oxygen, and you may feel tired, foggy, short of breath or notice reduced exercise performance. When it is higher than ideal, blood can become more concentrated, which may increase workload on the heart and raise other risks over time. Tracking Hb alongside RBC and ferritin over months and years helps you see trends, not just single snapshots.

Haemoglobin reflects both red cell production and iron availability. Persistently low Hb is often driven by iron deficiency but can also relate to insufficient B-vitamins (B12, folate, riboflavin), blood loss, or chronic inflammation. Persistently high Hb can be influenced by factors like living at altitude, dehydration, smoking, or sleep-disordered breathing. Because these influences are modifiable, Hb is a useful biomarker to optimise and to watch over the long term.

Haemoglobin levels can change with hydration, oxygen demand, and nutrient status. Common influences include:

• Iron and B-vitamin intake: Low iron, B12, or folate reduce haemoglobin production; adequate intake supports optimal levels.

• Hydration status: Dehydration concentrates the blood and can make Hb appear higher; overhydration can dilute it.

• Blood loss: Heavy menstrual bleeding, digestive bleeding, or frequent blood donation can lower Hb.

• Inflammation or chronic illness: Can suppress red blood cell production and reduce haemoglobin.

• Smoking and altitude: Both increase Hb as your body adapts to lower oxygen availability.

• Exercise and training load: Intense endurance training can temporarily lower Hb due to plasma expansion, while resistance training may improve red cell production.

• Sleep and respiratory health: Sleep apnea or disordered breathing at night can elevate Hb over time.

Before making any conclusions about haemoglobin, be sure to check related markers (RBC, ferritin, B12, folate) to see what might be causing the changes. Then, make any needed lifestyle adjustments and recheck your results to see if things improve.

If your haemoglobin is low

• Ensure you get adequate dietary iron intake. Include heme-iron foods (beef, lamb, mussels, sardines, chicken thighs). If you eat a plant based diet, pair legumes, tofu, wholegrains or leafy greens with vitamin C sources (citrus, capsicum, tomato) to enhance non-heme iron uptake. Avoid tea or coffee with meals; classic human studies show they can cut non-heme iron absorption by about 39% with coffee and ~64% with tea when consumed at the same meal. Leaving about 1 hour between a meal and tea meaningfully reduces this effect.

• Consider lactoferrin as a gentler iron helper. A clinical meta-analysis found oral bovine lactoferrin increased haemoglobin by ~11.8 g/L on average versus standard ferrous sulfate, with better tolerance in many studies. This can be a practical option if traditional iron upsets your gut.

• Layer supportive habits. Cook hydrating, iron-friendly meals and use longer simmer times for stews or tomato-based dishes, prioritise sleep, and build resistance training to support marrow health over time.
  
  

If your haemoglobin is high

• Hydrate consistently. Even mild dehydration concentrates blood and can nudge Hb upward on the day of testing. Consider a re-test under similar conditions. Try to test at a similar time of day and with a similar pre-test routine (hydration, caffeine timing, recent training) so you can compare like-for-like.

• Reduce smoking and improve sleep quality. Smoking and nocturnal breathing issues can raise Hb; improving airway health, nasal breathing, and sleep environment can help bring Hb back toward your personal baseline over time.

• Mind your environment. Spending long stretches at high altitude raises Hb; returning to lower altitude typically allows it to settle gradually.

Adult ranges vary slightly by lab.

Typical reference ranges:

• Women:

  • Optimal: 115–165 g/L

  • Mildly low: 110–114 g/L

  • Low: <110 g/L
    Elevated: >165 g/L

• Men:

  • Optimal: 125–185 g/L
    Mildly low: 120–124 g/L

  • Low: <120 g/L

Elevated: >185 g/L

1.  Anaemia, haemoglobin reference ranges, Australian Red Cross Lifeblood, 2024. Available from: https://www.lifeblood.com.au

2. Haemoglobin – factors that influence results, Pathology Tests Explained (Australia), 2023. Available from: https://www.pathologytestsexplained.org.au

3. Morck TA, Lynch SR, Cook JD. Inhibition of food iron absorption by coffee, The American Journal of Clinical Nutrition (American Society for Nutrition), 1983. Available from: https://www.sciencedirect.com/science/article/pii/S0002916523156796

4. Samavat A, et al. A 1-h time interval between an iron-containing meal and tea attenuates inhibition of iron absorption, The American Journal of Clinical Nutrition (American Society for Nutrition), 2018. Available from: https://ajcn.nutrition.org/article/S0002-9165(22)02698-3/fulltext

5. Zhao X, et al. Comparative Effects between Oral Lactoferrin and Ferrous Sulfate on Iron-Deficiency Anaemia: Meta-analysis of Clinical Trials, Nutrients (MDPI), 2022. Available from: https://www.mdpi.com/2072-6643/14/3/543