What Is Hyponatremia?

Hyponatremia is a condition that develops from low levels of sodium in the blood. Let's find out why it occurs, what its symptoms are, and what you can do to treat it.
What Is Hyponatremia?

Last update: 19 July, 2021

Hyponatremia is a disorder that occurs when there’s an imbalance in sodium levels in the body. It’s estimated to be the most common electrolyte homeostatic disorder of all. It occurs when the mineral values are less than 135 mEq / L (milliequivalents per liter).

Among other things, sodium is responsible for controlling acidity during digestion, maintaining a water balance, participating in the functioning of the nerves, regulating blood pressure, and is key in the functioning of cells. Its imbalance leads to the generation of various disorders in the body.

Although people get enough sodium from a balanced diet, various conditions, habits, or medications can cause the body to take in less than it should. Let’s get to know everything related to this condition: symptoms, causes, diagnosis and how to treat it.

Symptoms of hyponatremia

Common symptoms of hyponatremia
Nausea and vomiting are very characteristic of both hyponatremia and hypernatremia.

Under normal conditions, hyponatremia doesn’t produce any type of symptoms in patients. If the decrease in values is made progressively, it rarely manifests itself through external signs. The story is different when the decline is accelerated or reaches critical levels. In these cases you can experience:

  • Fatigue or lethargy
  • Sickness
  • Vomiting
  • Headaches
  • Muscle spasms
  • Irritability
  • Confusion, feeling dizzy, and loss of cognitive ability
  • Low blood pressure
  • Lack of appetite
  • Seizures

Their presence varies with each patient and depends on how the body reacts to sodium levels. It’s known to also manifest itself through falls and lack of balance, regardless of electrolyte values. Evidence indicates that if not treated properly, it can be fatal.

In general, the manifestation of symptoms varies according to the type of hyponatremia developed by the patient. They are usually divided into the following types:


This occurs when there’s an increase in the concentrations of water and sodium in the body. However, the water levels are higher, and this creates an electrolyte imbalance.

As the evidence indicates, this encourages edema to be produced. Other symptoms of hypervolemic hyponatremia are high blood pressure (hypertension) and ascites.


This is characterized by an increase in water levels in the body, without there being an increase in sodium. The symptomatic manifestation is concentrated in decreased urinary output and peripheral edema.


In this case, there’s a loss of water and sodium in the body, but with a greater excretion of the electrolyte. The characteristic symptoms of this variant are dry mucous membranes and skin, hypotension, tachycardia, and weight loss.

The absence and presence of the signs in each variant depends on the degree of evolution of the homeostatic disorder. It’s usually classified as mild (130-134 mEq / L), moderate (125-129 mEq / L) and severe (less than 125 mEq / L). The greater the decline, the greater the manifestation of the signs and the danger of collateral damage.

Causes of hyponatremia

To date, several catalysts that can cause hyponatremia have been identified. These can be due to day-to-day habits or underlying conditions that generate it. Let’s see what the main triggers of this disorder are:

Medication intake

Experts documented the relationship between the development of hyponatremia and intake of some groups of drugs. Those indicated are diuretics, antidepressants, antiepileptic, antibiotics, non-steroidal anti-inflammatory drugs, and proton pump inhibitors.

The case of diuretics is especially interesting. To our knowledge, almost in parallel with their introduction in 1957, thiazide diuretics were shown to be a direct cause of the disorder. These can inhibit sodium transport and prevent them from fulfilling their conventional function.

Doing excessively physical activity

Hyponatremia in athletes
Dehydration and electrolyte disorders such as hyponatremia can appear in some athletes during high-intensity exercise.

Research and studies indicate that episodes of extreme physical activity can trigger irregularities in electrolyte levels.

The relationship isn’t yet clear, but it’s believed that it may be due to the loss of the minerals through sweat and high fluid intake (or lack of it). It’s more common in high endurance activities, for example, marathons and triathlons.

Maintaining a poor diet and drinking a lot of beer

Although rare, diets very low in protein and other essential nutrients have been linked to low sodium concentrations. Most people get the required amount of sodium from their diet.

The Food and Drug Administration (FDA) says that this should be around 2,300 milligrams a day. However, in cases of malnutrition, there may be an imbalance.

It has also been found that the disorder can develop in people who drink a lot of beer. This disorder is sometimes called beer potomania and often occurs in the company of low sodium intake.

Being dehydrated

Paradoxically, in contrast to high alcohol consumption, dehydration can also trigger episodes of this type. When this happens it’s called hyponatremic dehydration and it’s more common than you think. For example, diarrhea and vomiting that occurs for several days can trigger this electrolyte condition.

Have a kidney condition

The kidney is in charge of filtering and eliminating water from the body. When there’s an imbalance in their functions, too much water can accumulate, which leads to an imbalance in sodium values. Kidney failure, kidney disease, renovascular hypertension, and many other conditions can be to blame. This is what several studies and investigations report to us.

Heart and liver conditions

These conditions can interfere with the body’s natural function of excreting excess water. Heart failure and cirrhosis, for example, can raise blood pressure. To treat this collateral damage, drugs such as diuretics are usually prescribed, which, as we have seen, are responsible for many of these disorders.

Special mention should be made of the syndrome of inappropriate antidiuretic hormone secretion (SIADH). This causes the body to retain water, which unbalances the electrolyte values. Their relationship is widely documented; in fact, treatment for hyponatremia is common in patients with this syndrome.

Other possible causes for electrolyte disorder include the following:

  • Anemia
  • Recreational drug abuse
  • Aging
  • Adrenal insufficiency (Addison’s disease)
  • Hypothyroidism
  • Diabetes insipidus

Among the main complications, we can highlight brain inflammation, a problem that can lead to commas or even death. Those who are among the associated risk factors should pay attention to their levels or the possible symptoms outlined.

Diagnosis of hyponatremia

The diagnosis of hyponatremia begins with a general assessment of the patient’s condition and medical history. The specialist will look for possible associations or causes and will check to see if the person is suffering from any of the related diseases.

Since a diagnosis cannot be carried out just based on the above, they’ll ask for urine and blood tests to determine the exact electrolyte value.

Thus, a measurement of serum sodium, serum osmolality, urine osmolality, urine electrolyte to serum ratio, urine sodium, fractional sodium excretion, uric acid and creatinine concentrations, and so on will help determine the disorder.

Based on all this, you will also be able to figure out what’s causing it. Sometimes, CT scans, MRIs, chest X-rays, thyroid profile, and other complementary tests can be done.

Treatment for hyponatremia

Treatment for this condition usually concentrates on counteracting the underlying cause. A personalized treatment plan will be applied, aimed at dealing with the causes that generate the imbalance. Some of the things that the specialist may suggest are the following:

  • Reducing your fluid intake
  • Modifying the dose of diuretics or change these to other drugs
  • Increasing sodium intake in the diet
  • Taking medicine to treat symptoms (headaches, nausea, and so on)

The above applies, in principle, to mild or moderate cases. If your condition is serious, they’ll choose to balance sodium levels through intravenous supplements. This should be done with extreme caution, as studies show that proceeding quickly and without dose adjustment can increase the risk of brain damage.

The specialist may also prescribe special medications to help with sodium retention. If there’s kidney, heart, or liver damage, the doctor will start an appropriate treatment.

Hyponatremia is a preventable disorder. In general, maintaining a healthy lifestyle, being aware of the symptoms generated by the intake of medications and hydrating moderately are all key to this.

If you’re part of the risk groups, talk to your doctor about the chances of developing the disease and monitor these values from time to time.

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