Hyponatremia: what it is, neurological symptoms and treatment

What is hyponatremia?

Hyponatremia is a metabolic disorder caused by an imbalance in the body that leads to a very low concentration of sodium in the blood . In other words: there is either too much water, or there is sodium deficiency in the body.

It can be mild, causing uncomfortable symptoms, or severe, leading to coma and even death.

Fortunately, the disease is curable . Its treatment may involve changes in diet, decreased water intake or use of diuretic medications, in more severe cases. It is worth remembering, however, that hyponatremia can not be treated simply with homemade solutions or with a higher sodium intake in the diet. It is always necessary, first of all, to seek professional guidance.

It is the most common hydroelectrolytic disorder in hospitalized patients. It is associated with a series of problems, such as the need for hospitalization in an intensive care unit and prolonged and costly hospitalization.

It differs in 5 variations, ranging from the least symptomatic to the most symptomatic. Its most severe complications can involve problems in the brain and neural transmissions, causing symptoms such as parkinsonism.

However, it is easily identifiable and, in its less severe versions, can be easily treated. Therefore, read the text to the end and watch for signs that may indicate the presence of this disease.

What is osmotic pressure?

The cells in our body are composed of water and other elements. In order to regulate and guarantee its proper functioning, it is necessary that each cell controls the water levels within it.

The cell does this control through a process called “osmosis”. In this process, the water changes from a less concentrated solution to a more concentrated (or less diluted), thus balancing the water levels on both sides (in the case of the human body, the extracellular and intracellular compartments).

The problem is that, if osmosis occurs in excess, both on one side and on the other, the amount of water in the cell becomes unbalanced, which can cause the cell to even burst, or “wither”.

This is where osmotic pressure comes in: it is the pressure that must be exerted on a system to prevent osmosis from occurring in excess.

Osmolalidade e osmolaridade

Both osmolality and osmolarity are terms that seek to designate the amount of osmotically active molecules in a solution . The difference between them is that osmolality refers to the number of milliosmoles per liter of solution, while osmolarity refers to the levels of milliosmoles per kilogram of water.


In general, there are 5 types of hyponatremia. With the exception of pseudohyponatremia and hypertonic hyponatremia, the disease occurs because there is more water than sodium in the body, which causes water to be in excess, both in the intracellular and extracellular compartments, diluting the sodium in the body.

The types of hyponatremia differ, basically, by the way they manifest themselves. Check out:

Evolemic hyponatremia

Euvolemic hyponatremia occurs when total water levels in the body are above normal and, in contrast, sodium levels remain the same.

In such cases, there is a modest increase in the volume of extracellular fluid, but not enough to cause edema (swelling by accumulated fluid). They are usually asymptomatic.

Hypervolemic hyponatremia

Hypervolemic hyponatremia occurs when both total water and sodium levels are higher than normal, but water levels are higher than sodium levels.

In this case, the volume of extracellular fluid is markedly increased, causing edema .

Hypovolemic hyponatremia

Hypovolemic hyponatremia occurs when the body loses water and  sodium, but the levels of sodium loss are higher than those of water.

Hypertonic hyponatremia (redistributive)

Hypertonic hyponatremia, or redistributive, is characterized by unchanged levels of water and sodium in the body. What happens is that the osmotic pressure increases in the extracellular layer, causing the water to move from the intra to the extracellular compartment, diluting the sodium in the body.

This variation of the disease can be easily seen in cases of hyperglycemia and can be fatal.


In pseudohyponatremia, an excess of lipids or proteins dilutes the aqueous phase of the extracellular compartment and the sodium levels decrease. The water and sodium levels in the body remain unchanged and there is no movement of liquids between the compartments.


Sodium is a component most commonly found outside cells. It is a very important electrolyte for maintaining the proper functioning of the body, for regulating blood pressure and for neurons, muscles and other organs in the body to function properly.

Hyponatremia occurs when the levels of sodium concentration in the body become very low. Therefore, people who face vomiting and chronic diarrhea are the most commonly affected by the problem: during these conditions, the body loses a lot of sodium, decreasing its concentration in the extracellular compartments.

When the sodium concentration outside the cell decreases a lot, for example, the body tries to balance this gap by sending water into the cells, which can cause them to swell and even burst. Neuronal cells are the most affected by this phenomenon.

The amount of normal sodium in the body varies between 135 and 145 mEq / L (mEq = milliequivalent). Below that it is considered a case of hyponatremia.

There are several factors that can lead to hyponatremia. People who have heart problems, such as heart failure, are more likely to acquire the problem, as are people who have kidney failure, cirrhosis , and who use diuretics or vasopressins.

This is because such diseases may be related to a deficit of sensitivity in the receptors present in the chest, kidneys and blood vessels, the main responsible for the detection of sodium drop in plasma.

When this deficit occurs, the precision in the production of Antidiuretic Hormone (ADH) is compromised in the neurohypophysis, which leads to the dysregulation of sodium levels in the body.

People who suffer from Syndrome of Inappropriate Antidiuretic Hormone (SIADH)  are more likely to experience hyponatremia.

SIADH happens when there is an excessive release of ADH in the body.

In addition, other diseases that cause hormonal changes in the body, such as Addison’s Disease, affect the ability of the adrenal glands to produce hormones that help maintain the optimal sodium balance in the body, causing hyponatremia.

Excessive water intake is another cause for the problem. When you drink a lot of water, the sodium levels are unbalanced. The same occurs with cases of dehydration, but for the opposite reason, that is, the loss of water and electrolytes.

Hypovolemic hyponatremia

As stated earlier, in this variation of the disease, there is a decrease in the total water levels in the body, with a relatively greater reduction in sodium.

It is caused by:

  • Gastrointestinal losses , caused by diarrhea or vomiting, for example;
  • Losses in the third space , such as burns, pancreatitis, peritonitis, rhabdomyolysis and small bowel obstruction;
  • Renal losses , such as use of diuretics, mineralocorticoid deficiency, osmotic diuresis, interstitial nephritis, cystic spinal disease, partial urinary tract obstruction, etc.

Evolemic hyponatremia

In these variations, there is a significant increase in the total water levels in the body, with the total sodium levels remaining almost unchanged.

Its causes are:

  • Use of drugs , such as diuretics, barbiturates, carbamazepine, chlorpropamide, clofibrate, opioids, vincristine, being more commonly associated with cyclophosphamide, NSAIDs (NSAIDs) and oxytocin;
  • Changes in the body , such as adrenal insufficiency, Addison’s disease, hypothyroidism and the syndrome of inappropriate ADH secretion;
  • Increased fluid intake ;
  • Increased release of ADH , which can be caused by emotional stress, pain and post-operative states.

Hypervolemic hyponatremia

This variation occurs when there is an increase in the total sodium levels in the body, with a relatively greater increase in water.

It occurs because of:

  • Extra-renal diseases , such as cirrhosis and heart failure;
  • Kidney diseases , such as acute renal failure, chronic nephropathy and nephrotic syndrome.

What is the function of sodium in the body?

The main function of sodium in the body is to regulate the amount of extracellular fluid, as well as the volume of blood plasma. In addition, it acts in the conduction of impulses in the nervous system and in the control of muscle contraction.

When the amount of sodium is at a lower level than normal, symptoms such as hypotension (low blood pressure), cramps, dehydration, dry mouth and vomiting may be present, as the amount of water in the cells increases, which can bring serious health risks.

Risk factors

All human beings need to consume enough water on a daily basis to keep their bodies healthy. However, water intake levels should be checked to make sure they are balanced and do not cause any problems.

However, there are some factors that can cause sodium levels in the body to be disrupted. Among them are:


Older people are more likely to be affected by hyponatremia. Especially those who have heart failure. This is because they have an elevation of the atrial natriuretic peptide hormone, produced by the cells of the heart. The higher the levels of this hormone, the higher the rate of sodium excretion.

In addition, the elderly have a lower amount of vasopressinase, an enzyme that cuts off the action of ADH and regulates sodium levels in the body, which makes them have to take vasopressins, which can be one of the causes of the disease.

Therefore, these people should, of course, take more medicines, they are more likely to develop a chronic disease that changes the sodium balance in the body.

Medicines and drugs

The use of certain medications, such as diuretics, antidepressants and pain relievers, can increase the flow of urine and sweat, the two main responsible for the loss of sodium in the body.

In addition, the recreational use of ecstasy also causes a drop in sodium levels in the body, as its use causes a lot of thirst. When the person is under the influence of this drug, he drinks more water, which decreases the concentration of sodium in the body.

Intense physical activity

People who practice intense physical activity suffer from the loss of electrolytes, such as sodium, all the time through sweating. This causes a lot of thirst, which causes the person to consume a lot of water, leading to hyponatremia.

It is very important that, during intense physical activities, drinks are made specifically for electrolyte replacement.


AIDS patients are also at an increased risk of being affected by the disease. To get a sense, hyponatremia is reported in more than 50% of patients hospitalized with AIDS.

This is because adrenal insufficiency has become increasingly common in AIDS patients, which can lead to SIADH and further worsen the condition of people affected by the virus.


When sodium levels in the extracellular portion decrease, water enters cells, causing them to swell. If this occurs in the brain, cerebral edema may be present.

Cerebral edema is very dangerous because the brain is confined within the skull, with no room to expand. This swelling can cause brain damage as the intracranial pressure increases.

The neurological symptoms  are very general and can include:

  • Headache;
  • Confusion;
  • Convulsions;
  • Restlessness and irritability;
  • Confusion;
  • Decreased consciousness, which can lead to coma and death.

In addition, other symptoms that may occur are:

  • Nausea;
  • Vomiting;
  • Muscle fatigue;
  • Spasms;
  • Cramps.

How is Hyponatremia diagnosed?

There are three laboratory tests that can be done to diagnose hyponatremia. When done in conjunction with the analysis of the patient’s history and standard physical examination, they are effective in detecting the disease and help to treat it when it is in its early stages.

The disease can be diagnosed by different types of medical specialties. A general practitioner can detect the disease, as well as hematologists, endocrinologists, neurologists and cardiologists.

Urinary osmolality test

It’s like a normal urine test. In it, a sterile urine sample is analyzed. To do this, women must clean the vulva and urethra, and men, the glans. Just release the stream of urine in the container given by the laboratory until it fills up and take the sample to be analyzed.

Normal results range from 500 to 850 millimoles per kilogram of urine, but it can be slightly above that range. If you have restricted liquids 12 to 14 hours before the test, the result is likely to exceed 850 millimoles.

Blood osmolality or serum osmolality test

The test is simple: it is enough for the patient to allow a healthcare professional to collect a small blood sample. It measures the amount of various substances in the serum (liquid part of the blood), including sodium.

In general, it is usually necessary to fast for 6 hours before the exam. Some medications, such as mannitol, can interfere with the results and, therefore, the patient must inform the doctor if he is using any medication.

Normal results are between 275 and 303 millimoles per kilogram of serum. The exact standards for normal results may vary by doctor and laboratory. In case of doubt, the doctor should always be consulted.

Urinary sodium level test

The urinary sodium level test is done to check the patient’s hydration status and also to assess kidney function.

There are two types of tests: a random test on a single urine sample, and a 24-hour test, which examines urinary sodium throughout the day.

As with the urinary osmolality test, just collect a urine sample in a sterile container and take it to the laboratory for further analysis.

In the 24-hour test, the patient must urinate in a special container every time he urinates.

What to expect during the medical consultation?

If you suspect hyponatremia, seek immediate medical help. The sooner you know about the disease, the easier it will be to treat your symptoms and the less likely you are to develop a severe condition.

During your doctor’s appointment, talk about your suspicions and describe your symptoms if you are experiencing headache , nausea, weakness or cramps.

Don’t forget to talk about your history and any information that can help your doctor diagnose hyponatremia. List the medications, vitamins , supplements and any other remedies, natural or pharmacological, that you are taking.

If you are feeling confused because of the symptoms of the disease, ask for help from a close friend or family member. They will be able to follow the previous steps more efficiently than you can on your own.

Does hyponatremia have a cure?

Fortunately, hyponatremia is curable . Its treatment is usually not very complicated and involves the replacement of sodium in the body.

What is the treatment?

In general, there are different approaches for each type of hyponatremia.

Hypovolemic hyponatremia

In hypovolemic hyponatremia, the patient can be treated with decreased fluid intake.

In addition, adjustments to diet, lifestyle and medication can help. Adding more sodium to the diet, for example, is one of the recommendations that the doctor can give to prevent  the onset of the problem. Drinking less water and stopping diuretics can also improve a patient’s health.

However, there are some specific types of treatment for people with more severe cases of hyponatremia. The options, in these cases, include the application of intravenous fluids with a sodium-rich solution in order to raise the levels of the substance in the bloodstream.

In the most severe cases, which can involve seizures and other complications, a 3% saline solution can be administered.

The use of some medications such as analgesics for headache and anticonvulsants may be indicated.

Evolemic hyponatremia

In cases of euvolemia, treatment is directly directed to the cause of the problem. If it is caused by hypothyroidism , for example, hypothyroidism is treated instead of hyponatremia itself. If it is not possible to treat the direct cause of the problem or it is not possible to deprive the patient of fluids, the use of certain medications may be necessary.

Hypervolemic hyponatremia

In cases of hypervolemia, the use of drugs that increase sodium levels in the body can be indicated, as in the case of hypovolemia, in which intravenous solutions are part of the treatment.

Water deprivation and intravenous fluid injection

This treatment consists of administering isotonic saline solutions to replace the intravascular volume. It is possible that, in addition to sodium replacement, there is a replacement of potassium, which is also an osmotically active substance.

For euvolemic patients, water restriction may be an option. In this treatment, you should restrict your water intake to less than 1L per day.

Pharmacological treatment

In patients with hypervolemia and euvolemia, vasopressin antagonists are indicated, which are used for intravenous administration. These drugs are contraindicated for hypovolemic patients, as they induce diuresis of water and sodium, which is not good for patients who have a lack of water in their blood (just the case of hypovolemia).

Medications for Hyponatremia

In the most common cases of hyponatremia, which are less severe, the use of medications is not so necessary. However, to treat more severe cases, the use of certain drugs may be indicated. They include:

  • Demeclociclina;
  • Lithium ;
  • Vaptans: Tolvaptan, Conivaptan, Satavaptan, Lixivaptan;
  • Furosemide .

Demeclocycline and lithium

Both lithium and demeclocycline are medications that have the side effect of opposing the action of ADH, a hormone responsible for preventing diuresis, which increases the urinary excretion of free water.


Vaptans are inhibitors of vasopressin V2 receptors. They are capable of promoting electrolyte-free water diuresis, such as sodium. They can be administered orally (Tolvaptan) or intravenously (Conivaptan, Satavaptan and Lixivaptan).

These drugs elevate serum sodium in patients with hypervolemic hyponatremia, causing the osmolarity of the cells to regulate and return to normal.

For now, they are only available for clinical use in the USA, as clinical studies show that these drugs improve symptoms, but do not reduce the mortality rate from the disease.


Furosemide, like other medications, is in the class of diuretics, and helps the body to get rid of excess water without the excretion of electrolytes such as sodium, improving cell osmolarity.


NEVER  self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

Living / Prognosis

After diagnosing hyponatremia, you may need to make some lifestyle changes.

If you eat low-sodium foods, for example, it may be worthwhile to start adding more salt to your diet. Remembering that it is not to exaggerate, too, because the excess salt can cause numerous health problems.

Water intake can be decreased. If you are one of those people who drink a lot of water, be aware, because the excess liquid can be harmful, because they dilute the sodium present in the blood too much.

A tip is to consume fruits rich in water, such as watermelon or melon. They help quench your thirst and are rich in nutrients that are good for your health!


Brain edema

When the osmolarity of neural cells becomes unregulated, brain cells can begin to swell, causing brain edema and causing the intracranial space to become increasingly tight.

This swelling of the brain can lead to serious problems, such as tumors, abscesses, bruises, anoxia (lack of oxygen), meningitis, encephalitis and intoxications. Intracranial pressure also increases, increasing the risk of brain hernias and other complications.

When sodium concentrations decrease very quickly within a 24- to 48-hour period, brain edema becomes more severe, leading to brainstem herniation, respiratory arrest and death.

Osmotic demyelinating syndrome

The main and most feared complication caused by hyponatremia is the osmotic demyelinating syndrome (formerly called pontine myelinolysis). It can happen as a consequence of the treatment of the disease and deeply affects the cells of the Central Nervous System (CNS).

It occurs when the treatment is very abrupt, causing the cells of the CNS to adapt in order to decrease the osmolarity of the intracellular medium, so that it becomes similar to that of the extracellular medium.

This causes damage to the myelin sheath, a structure responsible for assisting neural transmissions, to be damaged, which can lead to serious complications, such as:

  • Spastic tetraparesis (cerebral palsy);
  • Pseudobulbar paralysis (problems with swallowing, speech and spasms);
  • Agitation;
  • Emotional lability (sudden mood swings);
  • Paranoia;
  • Coma;
  • Ataxia (lack of coordination of muscle movements and loss of balance);
  • Parkinsonismo;
  • Urinary incontinence.

To prevent these problems from happening, sodium replacement should be gradual and slow, and it is very important to keep this pace steady during the first 24 hours of treatment.

However, in cases of more severe symptoms related to hyponatremia, the rhythm may be higher during the first hours of treatment, precisely to avoid more serious complications related to the disease itself.

How to Prevent Hyponatremia?

There are many ways to prevent hyponatremia. If you suffer from diseases that cause low blood sodium, such as adrenal gland failure, it is important to go to the doctor and take care of your symptoms.

Knowing the symptoms of hyponatremia is already a big step towards preventing it. Taking care when consuming diuretic products, for example, is a good choice.

If you are going to do intense physical activities, it is good to be aware of what you consume to replenish the water. There are two reliable ways to know how much water to drink: your thirst and the color of your urine. If you are not thirsty and your urine is yellowish but almost transparent, you probably do not need to drink more water.

In addition, it is a good question to ask your doctor if you should drink isotonic drinks instead of water when exercising. These drinks have high amounts of electrolytes and can help keep sodium levels in your body stable.

However, if you are not exercising with intensity or for long durations, it is likely that you will not need this replacement.

It is also very important to increase water consumption if:

  • The weather is very hot;
  • You are in a place of high altitude;
  • You are pregnant or breastfeeding;
  • You are throwing up;
  • You have diarrhea;
  • You have a high fever;

You should not drink more than 1L of water per hour. Don’t forget that drinking too much water in a short period of time can be bad for your health.

If you are an athlete, the ideal is to consume 150mL of water for each hour of exercise.

Hyponatremia is a curable disease, but it can lead to severe complications. So it is very important to be aware of the diet and water intake. Not worrying about these factors can even lead to death, so be smart!

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