Nephrology focuses on diagnosing and treating kidney diseases. The kidneys filter waste, balance fluids, regulate blood pressure, and manage acute and chronic conditions.
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The symptoms of sodium disorders are primarily neurological. Because sodium dictates the water balance in brain cells, any significant shift causes the brain to either swell or shrink. The severity of the symptoms often depends more on how fast the sodium level changes rather than the absolute number. A rapid drop can be fatal, while a slow decline might cause only mild fatigue. Recognizing these signs is crucial because they are often mistaken for general aging, dementia, or simple tiredness.
The causes are usually more complex than just “eating too much salt” or “not drinking enough.” They usually involve a failure of the body’s water regulation system. This impairment can be due to medications, organ failure, or hormonal imbalances. Understanding the root cause is the key to resolving the problem, as treating the symptom without fixing it often leads to a quick relapse.
When sodium levels drop, water moves into the brain cells. In the early or mild stages, the symptoms are non-specific. Patients often report nausea and a general feeling of malaise—just feeling “unwell.” A headache is common, which can range from a dull ache to a severe throb.
As the swelling increases, cognitive function declines. Patients may become confused, forgetful, or lethargic. Family members might notice personality changes or extreme sleepiness. In older adults, the condition can lead to unsteadiness and frequent falls, which is a major risk for fractures.
If the sodium level drops very low or very fast, the brain swelling becomes critical. This leads to seizures, hallucinations, and loss of consciousness (coma). The pressure inside the skull can eventually stop the brain stem from functioning, leading to respiratory arrest and death. This type of condition is why acute hyponatremia is a medical emergency.
High sodium means the brain cells are shrinking. The primary symptom is intense thirst. The body is screaming for water to dilute the salty blood. However, in people who cannot communicate thirst—like infants or stroke victims—this sign is missed.
Since hypernatremia is essentially severe dehydration, physical signs are prominent. The mouth and tongue become dry and sticky. The skin loses its elasticity; if you pinch it, it stays tented up. Urine becomes dark and sparse. The heart rate often increases (tachycardia) while blood pressure drops, causing dizziness when standing up.
As brain cells shrink, they become irritable. Patients may be jittery, restless, or agitated. Their muscles may twitch or spasm. In severe cases, just like with low sodium, the condition can progress to confusion, lethargy, seizures, and coma due to bleeding in the brain from torn vessels.
One of the most common causes of sodium disorders is the loss of body fluids. This can lead to either high or low sodium depending on what is lost more—salt or water.
Severe vomiting and diarrhea are major culprits. They cause the body to lose fluids rich in electrolytes. If you lose more water than salt, sodium goes up. Sodium decreases if you rehydrate with plain water without adding salt.
Medications prescribed for high blood pressure or heart failure, specifically thiazide diuretics, are a leading cause of hyponatremia in the elderly. These drugs compel the kidneys to excrete both sodium and water, which can sometimes lead to an imbalance.
Occasionally, the body holds onto too much water, which dilutes the sodium. This happens in chronic organ failures.
In congestive heart failure and liver cirrhosis, the body thinks it is dehydrated because blood flow is poor. It responds by aggressively hoarding water. This excess water dilutes the blood, leading to low sodium readings even though the total amount of sodium in the body is actually high. The condition is often accompanied by swelling (edema) in the legs and belly.
When kidneys fail, they cannot excrete excess water. If a patient drinks more fluid than their kidneys can remove, the sodium level drops due to dilution.
In some cases, the fluid volume in the body looks normal, but sodium is low. This is often due to SIADH (Syndrome of Inappropriate Antidiuretic Hormone).
In SIADH, the body produces too much antidiuretic hormone, telling the kidneys to retain water relentlessly. This dilutes the sodium. SIADH can be caused by many things, including lung cancer, head injuries, brain surgery, or medications like antidepressants and painkillers. Other hormonal issues, like severe hypothyroidism or adrenal insufficiency (Addison’s disease), can also disrupt sodium balance.
Occasionally, the cause is behavioral. Polydipsia is a condition where a person drinks excessive amounts of water, overwhelming the kidneys’ ability to pee it out. This symptom is seen in some psychiatric conditions.
Ecstasy (MDMA) use is another specific cause. The drug increases thirst and simultaneously causes the release of ADH, leading to water retention. This combination has caused fatal hyponatremia in young people at dance clubs. Conversely, elderly people who live alone may simply forget to drink or restrict fluids to avoid incontinence, leading to chronic dehydration and high sodium.
Send us all your questions or requests, and our expert team will assist you.
The headache is caused by mild brain swelling. As water moves into brain cells to balance the low sodium, it increases pressure inside your skull.
Indirectly, yes. Physical stress (like surgery or trauma) releases hormones that retain water. Severe pain and nausea also stimulate ADH release, lowering sodium.
For most people, no. The kidneys are excellent at conserving sodium. It is actually difficult to get hyponatremia just from a low-salt diet unless you are also starving or drinking massive amounts of water.
If your low sodium is caused by heart or liver failure, your body is retaining fluid. This excess fluid leaks into your tissues, causing leg swelling (edema).
Usually, the issue resolves once the medication is stopped. However, some drugs can cause long-term kidney changes that make you more susceptible to imbalances in the future.
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