University of Oxford

Hyponatremia – The Effects of Low Blood Sodium

Hyponatremia – or low blood sodium – is a common electrolyte imbalance in people over the age of 65. This is a condition where the blood level of sodium is abnormally low.

And now, new research has revealed that even mild hyponatremia is associated with higher rates of disability, heart attacks and death. This means that low blood sodium can serve as a marker of vulnerability to age-related diseases and conditions. (1)

Sodium is an electrolyte that helps regulate the fluid levels in your body. The right balance of sodium maintains normal blood pressure and keeps your nerves and muscles working properly.

When your body’s water level rises, sodium is diluted and cells begin to swell. Fluid accumulation is a burden on the heart and the kidneys and is especially dangerous to the brain since it has almost no room to expand.

Normal blood plasma levels have a sodium measurement of 136 to 145 milliequivalents per liter. When sodium falls below 135, hyponatremia occurs. (2)

Causes of Hyponatremia

There are a number of lifestyle factors and other conditions that can bring on hyponatremia, many of which are more common in older adults. A few of them are:

  • Diuretics – water pills work by excreting sodium from the body in urine
  • Chronic vomiting or diarrhea – your body loses fluid and electrolytes, including sodium
  • Diet – a low sodium diet combined with a high intake of water will disturb your fluid balance
  • Kidney problems – kidney failure impairs the body’s ability to remove excess fluid
  • Congestive heart failure – your abdomen and lower body retains fluid
  • Antidepressants and pain medication – these can cause you to urinate or perspire more than usual
  • Intense physical exercise – drinking too much water while taking part in long distance exercises like marathons, especially in hot weather, will dilute the sodium level of the blood (3)

A Surprising Effect of Hyponetremia

In older populations, breaking a bone is a serious health issue. A bone fracture is usually the result of a fall, but why is falling so much more prevalent in older adults? Hyponetremia may be one answer.

Falls are a major socioeconomic problem for older people – 30% of people over 65 will fall every year. This leads to bone fracture in 4-6% of cases and is a risk factor for admission to a nursing home facility. Falls are the leading cause of death and disability in this age group. (4)

A study published by the Oxford University Press identified hyponatremia as a single major risk factor for broken bones in older patients. (5)

An interesting conclusion of the study was two-fold…

  1. Even mild hyponatremia influenced older people both in terms of attention and their balance since symptoms include fatigue, lethargy, confusion and muscle weakness. This leads to a higher incidence of falls.
  2. Even after a fall is suffered, mild hyponatremia is not usually considered to be serious and thus goes untreated. The study found that patients were discharged from the emergency room or the orthopedic ward without the management of hyponatremia.

Researchers recommend that any senior who suffers a bone fracture as a result of a fall should have their blood level checked for low blood sodium. Future falls may be preventable if the condition of hyponetremia is addressed.

And please consult your health care provider before making any changes to your diet, exercise or supplement routine.


  1. Bourdel-Marchassona I, Laksira H, Pugeta E, “Interpreting routing biochemistry in those aged over 65 years: A time for change,”, Feb 2, 2010
  2. “Hyponatremia,”, July 14, 2009
  3. “Hyponatremia,”, July 14, 2009
  4. Kengnel FG, Andres C, Sattar L, Melot C, Decaux G, “Mild hyponatremia and risk of fracture in the ambulatory elderly,”, April 4, 2008
  5. Kengnel FG, Andres C, Sattar L, Melot C, Decaux G, “Mild hyponatremia and risk of fracture in the ambulatory elderly,”, April 4, 2008

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