Low sodium levels in the blood — a condition doctors call hyponatremia — happen when the sodium in your bloodstream drops below a safe range. Sodium plays a vital role in controlling fluid balance, nerve function, and muscle movement in your body. When levels fall too low, you may notice symptoms ranging from mild nausea to serious neurological problems. This article explains what causes low sodium levels, what symptoms to watch for, and how the condition is treated in Canada.
What Are Low Sodium Levels?
Sodium is an electrolyte — a mineral that carries an electrical charge in your body. It helps regulate how much water your cells hold and supports healthy nerve and muscle function.
Doctors measure sodium levels through a simple blood test. Normal sodium levels sit between 135 and 145 millimoles per litre (mmol/L). When your level drops below 135 mmol/L, you have low sodium levels, or hyponatremia.
This condition is more common than many people realize. It affects people of all ages, though older adults and those with certain chronic illnesses face a higher risk. According to Mayo Clinic’s overview of hyponatremia, it is one of the most common electrolyte imbalances seen in hospital settings.
Common Causes of Low Sodium Levels
Low sodium levels can develop for several different reasons. In general, they fall into two main categories: too much water in the body, or too much sodium lost from the body.
Too Much Water in the Body
When the body holds on to too much water, it dilutes the sodium in your blood. This is called fluid overload or overhydration. Several health conditions can trigger this.
Heart failure: A weakened heart pumps less effectively, causing fluid to build up in the body.
Kidney failure: Damaged kidneys cannot filter and remove excess water properly.
Liver cirrhosis: Scarring of the liver disrupts fluid regulation throughout the body.
SIADH (Syndrome of Inappropriate Antidiuretic Hormone secretion): The body produces too much of a hormone that tells the kidneys to retain water.
Drinking an extremely large amount of plain water in a short time can also cause low sodium levels. This is sometimes seen in endurance athletes who overhydrate during events like marathons.
Too Much Sodium Lost from the Body
In other cases, the body loses too much sodium rather than retaining too much water. This can happen through several routes.
Vomiting and diarrhea: Prolonged digestive losses can deplete sodium quickly.
Severe burns: Damaged skin loses large amounts of fluid and electrolytes.
Adrenal insufficiency (Addison’s disease): The adrenal glands fail to produce enough hormones that help the body retain sodium.
Certain medications: Diuretics (water pills), commonly prescribed for high blood pressure or heart conditions, can cause the kidneys to excrete too much sodium.
Furthermore, some hormonal conditions like hypothyroidism can also disturb sodium balance. Your family doctor can order blood tests to identify the underlying cause.
Symptoms of Low Sodium Levels
The symptoms of low sodium levels vary depending on how quickly sodium drops and how severe the deficiency becomes. Mild cases may produce only subtle warning signs, while severe cases can become life-threatening.
Mild to Moderate Symptoms
In the early stages, many people feel generally unwell but may not connect their symptoms to a sodium problem. Common early signs include:
Nausea or an aversion to drinking water
Headache
Fatigue and low energy
Muscle weakness or cramps
Vomiting
Irritability or restlessness
These symptoms can easily be mistaken for other conditions, such as the flu or dehydration. However, they should never be ignored, especially if they persist or worsen over time.
Severe Neurological Symptoms
When sodium levels drop significantly, the brain is especially vulnerable. Brain cells can swell as fluid shifts, causing serious neurological problems.
Confusion or disorientation
Difficulty concentrating or speaking clearly
Hallucinations
Seizures
Loss of consciousness or coma
As a result, severe hyponatremia is considered a medical emergency. If someone around you suddenly becomes confused, has a seizure, or loses consciousness, call 911 immediately. Do not wait to see if symptoms improve on their own.
For a detailed breakdown of neurological effects, Healthline’s guide to hyponatremia offers helpful and accessible information.
How Doctors Diagnose Low Sodium Levels
Diagnosing low sodium levels starts with a blood test called a basic metabolic panel or electrolyte panel. This test measures the amount of sodium in your bloodstream alongside other key minerals.
Your doctor may also order a urine test to check how much sodium your kidneys are excreting. This helps pinpoint whether the problem comes from fluid retention, sodium loss, or a hormonal imbalance.
Additional Tests Your Doctor May Order
Depending on your results, your doctor may investigate further. Additional tests can include:
Thyroid function tests (to check for hypothyroidism)
Adrenal hormone tests (to rule out Addison’s disease)
Kidney function tests
Imaging such as an ultrasound or CT scan if liver or heart disease is suspected
In Canada, your provincial health plan covers most of these blood and urine tests when ordered by a physician. If you do not have a family doctor, a walk-in clinic can order initial blood work to get the process started.
Treatment for Low Sodium Levels
Treatment for low sodium levels always depends on the underlying cause. There is no single one-size-fits-all approach. The goal is to raise sodium levels safely while treating whatever condition triggered the imbalance.
Treating Mild Cases
For mild hyponatremia caused by overhydration, your doctor may simply advise you to reduce your fluid intake. In some cases, adjusting or stopping a diuretic medication is enough to correct the imbalance.
If the cause is adrenal insufficiency or hypothyroidism, treating the underlying hormonal condition often restores sodium levels to normal over time. Your doctor will monitor your blood work closely during this process.
Treating Moderate to Severe Cases
Moderate or severe hyponatremia usually requires hospital treatment. Doctors raise sodium levels carefully using intravenous (IV) fluids. The correction must happen slowly and precisely.
Raising sodium levels too quickly is dangerous. It can cause a serious complication called osmotic demyelination syndrome, which can permanently damage nerve fibres in the brain. Therefore, hospital monitoring is essential for severe cases.
In cases caused by heart failure or liver cirrhosis, doctors manage the underlying disease alongside correcting sodium levels. This may involve diuretics, dietary changes, or other medications tailored to your specific condition.
Lifestyle and Dietary Adjustments
In some situations, dietary changes can support recovery and help prevent low sodium levels from recurring. Your doctor or a registered dietitian may recommend:
Moderating your daily fluid intake if overhydration is the cause
Adjusting your diet to include appropriate amounts of sodium-containing foods
Avoiding excessive water intake during exercise, particularly endurance sports
Using electrolyte drinks during prolonged physical activity instead of plain water
It is important to note that increasing dietary salt is not always the right solution. In fact, for many people with heart or kidney disease, too much sodium in the diet is harmful. Always follow the specific advice of your healthcare provider.
Who Is at Risk for Low Sodium Levels?
Certain groups of people face a higher risk of developing low sodium levels. Understanding these risk factors can help you and your doctor catch the problem early.
Older adults: Aging affects how the kidneys handle fluid and sodium, and many older adults take medications that increase risk.
People with chronic illnesses: Heart failure, kidney disease, liver disease, and hormonal disorders all raise the risk.
People taking certain medications: Diuretics, antidepressants (particularly SSRIs), and some pain medications have been linked to hyponatremia.
Endurance athletes: Drinking too much plain water during long races or events can dilute blood sodium levels rapidly.
People who experience prolonged vomiting or diarrhea: Gastroenteritis and other digestive illnesses can deplete electrolytes quickly.
According to Health Canada, older adults are particularly vulnerable to electrolyte imbalances and should have regular blood work as part of routine health monitoring.
When to See a Doctor
You should see your family doctor if you experience ongoing nausea, unexplained fatigue, muscle weakness, or confusion — especially if you have a known condition like heart failure, kidney disease, or liver disease.
If you do not have a family doctor, a walk-in clinic can order a blood test to check your sodium and electrolyte levels. Many provinces also offer telehealth services where you can speak with a nurse or doctor by phone or video at no cost.
Call 911 or go to your nearest emergency department immediately if you or someone else experiences seizures, sudden severe confusion, or loss of consciousness. These are signs of a serious medical emergency.
As always, this article is intended to inform, not to replace medical advice. Please speak with a qualified healthcare provider for a proper diagnosis and treatment plan suited to your individual health needs.
Frequently Asked Questions About Low Sodium Levels
What are the most common signs of low sodium levels?
The most common signs of low sodium levels include nausea, headache, fatigue, and muscle weakness. In more serious cases, symptoms can include confusion, seizures, and loss of consciousness. If you notice any of these symptoms, speak with your doctor or visit a walk-in clinic as soon as possible.
Can drinking too much water cause low sodium levels?
Yes, drinking excessive amounts of plain water in a short period can dilute the sodium in your blood and lead to low sodium levels. This is especially common in endurance athletes who drink large quantities of water without replacing electrolytes. Using a sports electrolyte drink during long events can help prevent this.
How are low sodium levels treated in Canada?
Treatment for low sodium levels in Canada depends on the underlying cause and how severe the deficiency is. Mild cases may be managed by adjusting fluid intake or medications, while severe cases require hospital care with IV fluids. Most diagnostic blood tests are covered under provincial health plans when ordered by a physician.
Which medications can cause low sodium levels?
Several common medications can contribute to low sodium levels, including diuretics (water pills), certain antidepressants such as SSRIs, and some pain medications. If you take any of these and notice symptoms like fatigue or confusion, speak with your doctor about monitoring your electrolyte levels through routine blood work.
Is low sodium a serious condition?
Low sodium levels can range from mild and manageable to life-threatening, depending on how low they drop and how quickly the drop occurs. Severe hyponatremia can cause brain swelling, seizures, and coma, making it a medical emergency. Early detection through regular blood work is the best way to catch and manage this condition safely.
Can low sodium levels go away on their own?
In some mild cases, low sodium levels may improve once the triggering factor is resolved — for example, after recovering from a bout of vomiting and rehydrating properly. However, most cases require medical evaluation to identify and treat the root cause. You should not assume low sodium will resolve without proper assessment by a healthcare provider.
Key Takeaways
Low sodium levels (hyponatremia) occur when blood sodium drops below 135 mmol/L.
Common causes include fluid overload from heart, kidney, or liver disease, as well as sodium loss through vomiting, diarrhea, or burns.
Symptoms range from nausea and fatigue in mild cases to seizures and coma in severe cases.
Diagnosis involves a simple blood test, which is covered by provincial health plans in Canada.
Treatment depends on the underlying cause and may range from adjusting fluids and medications to hospital care with IV sodium correction.
Older adults, people with chronic illnesses, and endurance athletes face the highest risk.
See your family doctor or a walk-in clinic if you have ongoing symptoms, and call 911 for any emergency neurological signs.
Always consult a qualified healthcare provider before making changes to your diet, fluid intake, or medications.
