Sodium

When low (hyponatremia, <135 mmol/L):

Common causes in athletes:

• Over-hydration (dilutional hyponatremia) -- drinking excessive water without electrolytes during training
• Excessive sweating with plain water replacement only
• Contest prep water/sodium manipulation protocols
• Diuretic use (furosemide, hydrochlorothiazide)

Management:

• Reduce plain water intake if over-hydrating; add electrolytes to water
• Sodium supplementation -- electrolyte drinks with 500-1000mg sodium per litre during heavy training
• Oral sodium -- salted foods, broth, or sodium chloride tablets (1-2g with meals)
• If on diuretics, monitor sodium closely and consider potassium-sparing alternatives
• Severe hyponatremia (<125 mmol/L) is a medical emergency -- seek immediate care

When high (hypernatremia, >145 mmol/L):

• Almost always dehydration -- increase fluid intake
• Common during aggressive contest prep water restriction
• Ensure adequate daily water intake (3-4L minimum for athletes)

References:

• Filippini, T., Naska, A., Kasdagli, M.-I., et al. (2020). Potassium intake and blood pressure: A dose-response meta-analysis. Journal of the American Heart Association, 9(12), e015719. DOI: 10.1161/JAHA.119.015719