Hyponatremia is a condition that occurs when the level of sodium in the blood is abnormally low.

Sodium is electrolyte, and it helps regulate the amount of water that’s in and around the cells. In hyponatremia, one or more factors – ranging from an underlying medical condition to drinking too much water during endurance sports – cause the sodium in the body to become diluted. When this happens, the body’s water levels rise, and the cells begin to swell. This swelling can cause many health problems, from mild to severe.


Hyponatremia treatment is aimed at resolving the underlying condition. Depending on the cause of hyponatremia, the patient may simply need to cut back on how much he drinks. In other causes of hyponatremia, patient may need intravenous fluids and medications.


Hyponatremia signs and symptoms may include:


  • Nausea and vomiting
  • Headache
  • Confusion
  • Loss of energy
  • Fatigue
  • Restlessness and irritability
  • Muscle weakness, spasms or cramps
  • Seizures
  • Unconsciousness
  • Coma


Sodium plays a key role in the body. It helps maintain normal blood pressure, supports the work of the nerves and muscles, and regulates the body’s fluid balance.


When the sodium level in the blood becomes too low, extra water enters the cells and causes them to swell. Swelling in the brain is especially dangerous because the brain is confined by the skull and unable to expand without causing symptoms.


A normal sodium level is between 135 and 145 milliequivalents per liter (mEq/L) of sodium. Hyponatremia occurs when the sodium in the blood fall below135 mEq/L.


The imbalance between sodium and water in the blood may occur in three primary ways:


– In hypervolemic Hyponatremia, the body has too much water. Hypervolemic Hyponatremia is commonly the result of kidney failure, heart failure or liver failure.

– In euvolemic Hyponatremia, the water level is too high. This condition is commonly due to chronic health conditions, cancer or certain medications.

– In hypovolemic hyponatremia, patients have too little water and sodium. This may occur, for example, when exercising in the heat without replenishing your fluid electrolytes or with marked blood loss.


Many possible conditions and lifestyle factors can lead to Hyponatremia, including:


– Certain medications. Some medications, such as antidepressants and pain medications can cause you to urinate or perspire more than normal.

– Water pills (diuretics)- especially thiazides diuretics. Diuretics work by making the body get rid of more sodium in urine.

– Cirrhosis. Liver disease can cause fluids to accumulate in the body.

– Kidney problems. Kidney failure and other kidney disease may make it hard to efficiently remove extra fluids from the body.

– Congestive cardiac failure. This condition causes the body to retain fluids.

– Syndrome of inappropriate anti- diuretic hormone (SIADH). In this condition, high levels of the anti-diuretic hormone (ADH) are produced, causing the body to retain water instead of excreting if normally in the urine.

– Drinking too much water during exercise (exertion hyponatremia). Because one loses sodium through sweat, drinking too much water during endurance activities, such as marathons and triathlons, can dilute the sodium content of the blood.

– Hormonal changes due to adrenal gland insufficiency (Addison’s disease). The adrenal glands produce hormones that help maintain the body’s balance of sodium, potassium and water.

– Hormonal changes due to an underactive thyroid (hypothyroidism). Hypothyroidism may result in a low blood- sodium level.

– Primary polydipsia. In this condition, the thirst increases significantly, causing the patient to drink too much fluid.

– The recreational drug Ecstasy. This amphetamine increases the risk of severe and even fatal cases of hyponatremia.

– Chronic, severe vomiting or diarrhea. This causes the body to lose fluids and electrolytes, such as sodium.

– Dehydration. In dehydration, the body loses fluids and electrolytes.

– Diet. Low- sodium, high- water diet can sometimes disturb the proper balance between sodium fluids in the blood.


The following factors may increase the risk of Hyponatremia:


– Age. Low blood sodium is more common in older adults. Contributing factors include age-related changes and a greater likelihood of developing a chronic disease that affects the bodies sodium balance.

– Certain drugs. Medications that increase the risk of hyponatremia include thiazide diuretics as well as some antidepressants and pain medications that cause the patient to urinate or perspire more than usual. In addition, the recreational drug ecstasy has been linked to fatal cases of hyponatremia.

– Conditions that increase the body’s water excretion. Medical conditions that may increase the risk of hyponatremia include kidney disease, syndrome of inappropriate anti- diuretic hormone (SIADH) and heart failure, among others.

– Diet. The patient may be at an increased risk of Hyponatremia if he/she is following a low sodium diet.

– Intensive physical activities. People who drink too much water while taking part in marathons, ultra marathons, triathlons and other long- distance, high intensity activities are at an increased risk of hyponatremia.

– Climate. New exposure to hot weather can increase the amount of sodium the patient loses through sweating during exercise.


In chronic Hyponatremia, sodium levels drop gradually over days or weeks – and symptoms and complications are typically more moderate.


In acute Hyponatremia, sodium levels drop rapidly – resulting in potentially dangerous effects, such as rapid brain swelling, which can result in coma and death.


Premenopausal women appear to be at the greatest risk of Hyponatremia – related brain damage. This may be related to the effect of women’s sex hormones on the body’s ability to balance sodium levels.


Because the signs and symptoms of Hyponatremia occur in many conditions, it’s impossible to diagnose the condition based on a physical exam alone. To confirm low blood sodium, doctor will order blood tests and urine tests.


Hyponatremia treatment is aimed at addressing the underlying cause, if possible.


If the patient has moderate, chronic Hyponatremia due to the diet, diuretics or drinking too much water, doctor may recommend temporarily cutting back on fluids. Doctor also may suggest adjusting the diuretic use to increase the level of sodium in the blood.


If the patient has severe, acute Hyponatremia, he/she will need more aggressive treatment. Options include:


– Intravenous fluids. Doctor may recommend intravenous (IV) administration of a sodium solution to raise the sodium levels in the blood. This often requires a stay in the hospital.


– Medications. The patient may take medications to manage the signs and symptoms of hyponatremia, such as headache, nausea and seizures.


– Hormone therapy. If adrenal gland insufficiency (Addison’s disease) is the cause of hyponatremia, the patient may take hormones to replace the deficiency.


The following measures may help the patient prevent hyponatremia:


– Treat associated conditions. Getting treatment for conditions that contribute to Hyponatremia, such as adrenal gland insufficiency, can help prevent low blood sodium.

– Educate yourself. If the patient has a medical condition that increases the risk of Hyponatremia or the patient takes diuretic medications, be aware of the signs and symptoms of low blood sodium. Always talk with the doctor about the risks of a new medication.

– Take precautions during high- intensity activities. Athletes should drink only as much fluid as they lose due to sweating during a race- usually no more than about 34 ounces ( about 1 liter ) of water an hour during extended exercise.

– Consider drinking sports beverages during demanding activities. Ask the doctor about replacing water with sports beverages that contain electrolytes when participating in endurance events such as marathons, triathlons and other demanding activities.

– Drinking water in moderation. Drinking water is vital for the health, so make sure you drink enough fluids. But don’t overdo it. Thirst and color of the urine are usually the best indications of how much water you need. If you are not thirsty and your urine is pale yellow, you are likely getting enough water.



Dr. A.K.M. Aminul Hoque
Associate Prof. (Medicine)
Dhaka Medical College & Hospital,


muzammel hoque

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