Sodium Levels: Meaning, Normal Range and Low Sodium Symptoms

Sodium is a key electrolyte that controls fluid balance, nerve signals, and muscle function. Normal sodium levels are typically 135–145 mmol/L. Low sodium levels symptoms (hyponatremia symptoms) include confusion, fatigue, and headaches, while high levels usually reflect dehydration. This blood test helps assess hydration, kidney function, and electrolyte balance.

Contents

→ Result interpretation
→ Check your value Sodium
→ What is Sodium
→ Reference ranges
→ Causes of abnormal values
→ Sodium in combination with other markers
→ Possible symptoms
→ When to see a doctor
→ What to do if abnormal
→ Frequently asked questions
→ Related markers

Result interpretation Sodium

What your result means based on common reference ranges

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Normal

Sodium levels within 135–145 mmol/L indicate balanced hydration, stable kidney function, and proper electrolyte regulation.

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Mildly elevated

Mildly elevated sodium levels suggest dehydration or increased salt intake affecting fluid balance and kidney regulation.

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Significantly elevated

Severely high sodium levels indicate significant dehydration or renal dysfunction, increasing risk of neurological complications.

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Below normal

Low sodium levels (hyponatremia) reflect fluid imbalance, often linked to kidney disease, SIADH, or excessive water intake.

🔬 Check your value Sodium

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Sodium, mmol/L

Sex

Age

What is Sodium?

Sodium is the main extracellular electrolyte responsible for maintaining fluid balance and blood pressure. In a blood test, sodium levels reflect how well the body regulates water and electrolytes through the kidneys and hormones such as aldosterone and ADH. Abnormal levels are commonly linked to dehydration, kidney disease, or hormonal disorders like SIADH. Low sodium levels symptoms often affect brain function due to cellular swelling, while high levels may indicate water loss. Monitoring sodium is essential for evaluating electrolyte imbalance, hydration status, and neurological risk.

Reference ranges

Group	Normal range	Unit
Men	135 – 145	mmol/L
Women	135 – 145	mmol/L
Children	138 – 145	mmol/L
Pregnant	130 – 140	mmol/L

Causes of abnormal values

Causes of low Sodium

• Excessive water intake — dilutes sodium concentration in blood
• Diuretics — increase sodium loss through urine
• Heart failure — fluid retention dilutes sodium levels
• Kidney disease — impaired regulation of sodium and water
• SIADH — abnormal hormone levels cause water retention and dilution

Causes of high Sodium

• Dehydration — water loss concentrates sodium levels in the bloodstream
• Excessive sweating — fluid loss without replacement increases sodium concentration
• High salt intake — excessive sodium consumption raises blood levels
• Diabetes insipidus — kidneys lose water excessively, concentrating sodium
• Medications (steroids) — promote sodium retention in the body
• Severe diarrhea — fluid loss reduces plasma volume and raises sodium

Sodium in combination with other markers

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Low Sodium + High Potassium Suggests adrenal insufficiency such as Addison's disease, affecting hormonal control of electrolyte balance.

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High Sodium + High Urea Indicates dehydration, where reduced plasma volume concentrates sodium and nitrogen waste products.

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Low Sodium + High Glucose Hyperglycemia pulls water into blood, diluting sodium levels and mimicking hyponatremia.

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Low Sodium + Low Chloride Often reflects fluid loss from vomiting or diuretics, impacting electrolyte balance and acid-base status.

Possible symptoms

•Headache and confusion
•Nausea and vomiting
•Muscle weakness or spasms
•Fatigue and low energy
•Seizures in severe hyponatremia

When to see a doctor

Seek medical advice if sodium levels fall below 130 mmol/L or rise above 150 mmol/L. Urgent care is needed if levels drop below 125 mmol/L with confusion, seizures, or drowsiness. Persistent symptoms of low sodium or abnormal trends in blood tests also require evaluation.

What to do if abnormal

💧 Adjust fluid intake based on medical advice
💊 Review medications like diuretics with a doctor
🧂 Modify salt intake only if clinically recommended
🩺 Treat underlying conditions such as kidney or heart disease
🔁 Repeat blood test within 24–48 hours if abnormal

The information on this page is intended for general understanding of test results and does not replace medical consultation. Accurate interpretation requires considering other blood markers and individual factors.

Content is based on medical literature and used within the PulseBook analytical system.

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Frequently asked questions

What are low sodium levels symptoms?

Low sodium levels symptoms include fatigue, confusion, headache, and nausea. In more severe cases, hyponatremia symptoms may involve seizures or loss of consciousness. These occur because water shifts into brain cells, causing swelling. Monitoring sodium levels in a blood test helps detect this early.

What is the normal sodium range mmol/L?

The sodium normal range mmol/L is typically 135–145 for adults. This range is consistent in most laboratories, including NHS standards. Slight variations may occur depending on hydration and lab methods, but values outside this range may require interpretation.

What does a sodium blood test tell you?

A sodium blood test evaluates fluid balance, kidney function, and electrolyte regulation. It helps detect dehydration, overhydration, or hormonal disorders. Abnormal sodium levels often indicate issues with water balance rather than total salt content in the body.

What is a dangerous sodium level?

A sodium level below 125 mmol/L or above 155 mmol/L is considered dangerous. These levels can affect brain function and lead to neurological complications. Immediate medical attention is required, especially if symptoms like confusion or seizures are present.

What causes low sodium levels in blood?

Low sodium levels in blood are usually caused by excess water retention, diuretics, kidney disease, or SIADH. The condition dilutes sodium rather than reducing total body sodium. Identifying the cause is essential for correct treatment.

Is sodium normal range UK different?

The sodium normal range UK is generally the same as international standards, typically 135–145 mmol/L. NHS labs may have slight variations, but interpretation remains consistent. Always compare results with the reference range provided by your laboratory.