Bilirubin
| Clinical | Optimal | |
|---|---|---|
| Male | 3 - 21 umol/L | 3-20 umol/L |
| Female | 3 - 21 umol/L | 3-20 umol/L |
What is Bilirubin?
Bilirubin is a yellow-orange pigment produced as a natural byproduct when your body breaks down old or damaged red blood cells. This process occurs primarily in the spleen, where the haemoglobin from red blood cells is converted into unconjugated (indirect) bilirubin, which then travels to the liver bound to albumin.
In the liver, bilirubin is processed (conjugated) and made water-soluble, then excreted into bile and eventually eliminated through your stools, which is what gives them their characteristic brown colour. A small amount also passes through the kidneys into urine.
Total bilirubin measured in a standard blood test includes both unconjugated and conjugated forms. When bilirubin levels rise significantly, it can cause a visible yellowing of the skin and eyes known as jaundice. However, mildly elevated bilirubin is very common and is often due to a harmless genetic condition called Gilbert's syndrome, which affects approximately 5-10% of the UK population.
Why Bilirubin Matters for Your Health
Bilirubin is a key indicator of how effectively your liver is processing and excreting waste products. Abnormal bilirubin levels can point to problems at various stages: excessive red blood cell breakdown, impaired liver processing, or blocked bile drainage.
Interestingly, mildly elevated bilirubin may actually be beneficial. Bilirubin is a potent antioxidant, and research suggests that individuals with Gilbert's syndrome (who have chronically mild bilirubin elevation) may have lower rates of cardiovascular disease and certain cancers. This is an active area of longevity research.
For monitoring overall liver health, bilirubin adds important context to your ALT, AST, and ALP results. A rise in bilirubin alongside other liver enzyme abnormalities can indicate more significant liver dysfunction and helps guide the urgency of further investigation.
Bilirubin& Your Wearable Data
Bilirubin is a breakdown product of haemoglobin from red blood cells. At mildly elevated levels, bilirubin actually acts as a powerful antioxidant with cardiovascular protective properties. Your wearable's activity data provides context: intense prolonged exercise can temporarily increase bilirubin through enhanced red blood cell turnover, particularly in endurance athletes.
Gilbert's syndrome, a benign genetic condition causing mildly elevated bilirubin, affects approximately 5-10% of the population. If your bilirubin is consistently mildly elevated but all other liver markers are normal, and your wearable data shows good cardiovascular fitness and recovery patterns, this is likely benign and may even be cardioprotective.
Hydration status affects bilirubin concentration. Wearable data showing intense training sessions or high activity days with potential dehydration may correlate with slightly higher bilirubin readings. Ensuring adequate hydration before blood tests, particularly if your wearable indicates high calorie expenditure the previous day, helps ensure accurate results.
What High Bilirubin May Suggest
Elevated bilirubin can result from increased red blood cell breakdown (haemolysis), impaired liver function, or obstructed bile flow. The pattern of elevation helps determine the cause. Unconjugated (indirect) bilirubin rises with haemolysis or Gilbert's syndrome, while conjugated (direct) bilirubin rises with liver disease or bile duct obstruction.
Gilbert's syndrome is by far the most common cause of mildly elevated bilirubin in the UK, affecting up to 10% of the population. It is a harmless genetic condition where the liver is slightly less efficient at conjugating bilirubin. Levels typically fluctuate and may rise with fasting, illness, or stress.
More concerning causes include hepatitis, cirrhosis, gallstones blocking the bile duct, and certain medications. If bilirubin exceeds 50 umol/L, jaundice becomes clinically visible. Very high bilirubin requires prompt medical evaluation to identify and treat the underlying cause.
What Low Bilirubin May Suggest
Low bilirubin levels are not generally considered clinically significant and are a normal finding. There is no established lower limit of concern for bilirubin in routine clinical practice.
Some research has suggested that very low bilirubin may be associated with reduced antioxidant protection, given bilirubin's role as an endogenous antioxidant. However, this is not an established clinical concern and would not typically prompt any action or investigation.
For most people, bilirubin at the lower end of the reference range simply reflects efficient liver processing and normal red blood cell turnover.
How to Optimise Your Bilirubin
Food
Support liver health with a varied diet rich in fruits, vegetables, whole grains, and lean proteins to ensure efficient bilirubin processing, Stay well hydrated, as adequate fluid intake supports bile production and bilirubin excretion, Include turmeric and bitter greens such as rocket, dandelion greens, and endive, which may support bile flow, Reduce alcohol consumption, which directly impairs the liver's ability to process bilirubin
Lifestyle
Avoid prolonged fasting if you have Gilbert's syndrome, as fasting can trigger temporary rises in bilirubin levels, Maintain a regular eating pattern with balanced meals to support consistent liver function, Stay well hydrated throughout the day to support bile production and kidney function, Ensure adequate sleep and stress management, as both illness and physiological stress can temporarily raise bilirubin
Supplements
Milk thistle (200-400mg daily) supports overall liver function and bile flow, which aids bilirubin processing, Artichoke leaf extract (300-600mg daily) has been shown to stimulate bile production and may support bilirubin excretion, Dandelion root extract may support liver and gallbladder function, promoting healthy bile flow
When to Speak to Your GP
See your GP if your bilirubin results suggest levels above 30 umol/L, particularly if accompanied by symptoms such as yellowing of the skin or eyes, dark urine, pale stools, abdominal pain, or itching. Seek urgent medical attention if bilirubin exceeds 50 umol/L or if jaundice develops suddenly. If mildly elevated bilirubin is found without other abnormalities, your GP may diagnose Gilbert's syndrome, which is benign and requires no treatment.
References
- NHS. Jaundice — Overview. Updated 2024. nhs.uk
- NICE. Non-alcoholic fatty liver disease (NAFLD): assessment and management. NG49. nice.org.uk
- BMJ. Fevery J. Bilirubin in clinical practice: a review. Liver Int. 2008;28(5):592-605. pubmed.ncbi.nlm.nih.gov
- Lancet. Vitek L, Tiribelli C. Bilirubin: the yellow hormone? J Hepatol. 2021;75(6):1485-1490. pubmed.ncbi.nlm.nih.gov
Medical Disclaimer— This content is for general educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Omniwo Ltd is a wellness information service and is not a medical device, clinical laboratory, or regulated healthcare provider under MHRA guidelines. The “optimal ranges” presented on this page are based on published clinical guidelines (WHO, NICE, NHS) and peer-reviewed research; they represent functional wellness targets and may differ from standard laboratory reference ranges. Individual results should always be interpreted by a qualified healthcare professional (such as your GP) who understands your full medical history. Do not start, stop, or change any medication or supplement based solely on this information. If you are experiencing symptoms, seek medical attention promptly.