Sodium
| Clinical | Optimal | |
|---|---|---|
| Male | 133 - 146 mmol/L | 136–145 mmol/L |
| Female | 133 - 146 mmol/L | 136–145 mmol/L |
What is Sodium?
Sodium is the most abundant electrolyte in the blood and extracellular fluid, playing a critical role in maintaining fluid balance, blood pressure, and proper nerve and muscle function. The body tightly regulates sodium levels through a complex interplay between the kidneys, adrenal glands, and pituitary gland.
Sodium levels in the blood are primarily controlled by antidiuretic hormone (ADH), aldosterone, and atrial natriuretic peptide. These hormones adjust how much sodium and water the kidneys retain or excrete to maintain concentration within a narrow range.
It is important to understand that blood sodium levels do not directly reflect dietary salt intake. The body's regulatory mechanisms are highly effective at maintaining blood sodium within normal limits, even with varying dietary intake. Abnormal blood sodium almost always reflects an issue with fluid balance or hormonal regulation rather than simple dietary excess or deficiency.
Why Sodium Matters for Your Health
Sodium homeostasis is essential for cellular function throughout the body. Even modest deviations from the normal range can cause significant symptoms, and severe abnormalities can be life-threatening. This makes sodium one of the most clinically important electrolytes to monitor.
For longevity and health optimisation, sodium monitoring helps detect kidney dysfunction, hormonal imbalances (particularly adrenal and pituitary), and medication side effects early. Chronic mild hyponatraemia (low sodium) is increasingly recognised as a condition that affects older adults and can contribute to falls, cognitive impairment, and osteoporosis.
Sodium testing is particularly valuable for anyone taking diuretics, ACE inhibitors, or other medications that affect fluid and electrolyte balance, as well as for those who exercise heavily or have conditions affecting the kidneys or endocrine system.
Sodium& Your Wearable Data
Sodium is the primary extracellular electrolyte, essential for fluid balance, nerve function, and muscle contraction. Wearable data is highly relevant for sodium status: exercise causes sodium loss through sweat (500-1500 mg per litre of sweat), and intense or prolonged training visible on your wearable increases depletion risk. Your exercise duration, intensity, and environmental conditions all affect sodium balance.
Exercise-associated hyponatraemia (dangerously low sodium) is a serious risk for endurance athletes. Wearable data showing prolonged exercise sessions (3+ hours) with high fluid intake but inadequate sodium replacement is a risk pattern. GPS and activity data from long runs, rides, or hikes, combined with environmental temperature data, helps identify when sodium supplementation during exercise is necessary.
Resting sodium levels are tightly regulated by the kidneys. Your wearable's hydration-related data (exercise load, heart rate recovery, resting heart rate) provides context for interpreting borderline sodium results. Chronic mild dehydration from high activity levels without adequate electrolyte intake may contribute to subtle sodium imbalances detectable on blood testing.
What High Sodium May Suggest
Elevated sodium (hypernatraemia) most commonly results from dehydration — not drinking enough water, excessive sweating, diarrhoea, or vomiting. Rarely, it may suggest diabetes insipidus (a condition affecting water retention), excessive salt intake in those with impaired thirst mechanisms, or certain kidney disorders.
Symptoms of high sodium may include intense thirst, confusion, restlessness, and in severe cases, seizures. Older adults are particularly vulnerable as the thirst mechanism may become less effective with age.
If results suggest elevated sodium, the most common and straightforward intervention is ensuring adequate hydration. Persistent hypernatraemia despite adequate fluid intake warrants further investigation of kidney and hormonal function.
What Low Sodium May Suggest
Low sodium (hyponatraemia) is the most common electrolyte abnormality encountered in clinical practice. It may suggest excessive fluid intake (dilutional hyponatraemia), syndrome of inappropriate ADH secretion (SIADH), adrenal insufficiency, hypothyroidism, or medication side effects (particularly from diuretics, SSRIs, and carbamazepine).
Mild hyponatraemia (130–135 mmol/L) may cause subtle symptoms including nausea, headache, fatigue, and poor concentration. Moderate to severe hyponatraemia (below 125 mmol/L) can cause confusion, seizures, and requires urgent medical attention.
Endurance athletes are at risk of exercise-associated hyponatraemia from excessive water intake during prolonged activity. If results suggest low sodium, your GP will assess fluid status, medications, and hormonal function to determine the cause.
How to Optimise Your Sodium
Food
For low sodium, ensure you are not excessively diluting your electrolytes with plain water — consider adding a small pinch of mineral-rich salt to water during and after exercise. Include naturally sodium-containing foods such as celery, beetroot, and olives in moderation. For high sodium, focus on reducing processed foods, which account for approximately 75% of dietary sodium in the UK diet. Increase potassium-rich foods (bananas, sweet potatoes, leafy greens), as potassium helps counterbalance sodium's effects on blood pressure. Ensure adequate overall hydration with water throughout the day.
Lifestyle
Drink water in response to thirst rather than forcing excessive intake, particularly during exercise. During prolonged endurance exercise, use electrolyte solutions rather than plain water. Monitor medications that may affect sodium levels and discuss any concerns with your GP. Maintain a balanced approach to salt intake — neither excessive restriction nor overconsumption. In hot weather or during illness with vomiting or diarrhoea, pay extra attention to electrolyte replacement.
Supplements
Electrolyte supplements containing sodium, potassium, and magnesium can be beneficial during intensive exercise, illness, or very hot weather. A high-quality mineral salt (such as Himalayan or Celtic sea salt) used in moderation provides trace minerals alongside sodium. Magnesium supplementation may support overall electrolyte balance.
When to Speak to Your GP
See your GP if sodium falls outside the reference range, even mildly, as the cause should be identified. Seek urgent medical attention if sodium is below 125 mmol/L or above 150 mmol/L, or if you experience confusion, seizures, severe headache, or significant neurological symptoms. If you are taking diuretics or other medications that affect sodium, regular monitoring is recommended.
References
- NHS. Dehydration — Overview. Updated 2024. nhs.uk
- NICE. Hyponatraemia — Clinical Knowledge Summaries. cks.nice.org.uk
- BMJ. Spasovski G, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Eur J Endocrinol. 2014;170(3):G1-G47. pubmed.ncbi.nlm.nih.gov
- NEJM. Sterns RH. Disorders of plasma sodium. N Engl J Med. 2015;372(1):55-65. 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.