Internal Medicine

Electrolyte Panel: Sodium, Potassium & Essential Minerals

Electrolytes are charged minerals dissolved in your blood and body fluids that control virtually every critical process in your body — from the nerve impulses that tell your heart to beat, to the muscle contractions that move your limbs, to the delicate acid–base balance that keeps your blood pH within a razor-thin 7.35–7.45 range. Sodium, potassium, chloride, bicarbonate, magnesium, phosphate, and calcium work together in precise ratios to maintain fluid balance, blood pressure, and cellular function. Electrolytes are part of virtually every standard blood test ordered in Australia, making them one of the most commonly measured and clinically important panels in pathology.

What Electrolytes Do

Each electrolyte has a specific primary role in the body. While they work together as a system, understanding what each one does individually helps explain why even small imbalances can cause significant symptoms.

Sodium

Regulates total body fluid volume and blood pressure
Conducts nerve impulses along neurons
Drives nutrient absorption in the gut (glucose, amino acids)

Potassium

Maintains heart rhythm and cardiac muscle contraction
Enables skeletal muscle contraction and relaxation
Supports nerve signal transmission

Chloride

Maintains acid–base balance with bicarbonate
Forms hydrochloric acid (HCl) for digestion
Regulates fluid balance across cell membranes

HCO₃

Bicarbonate

Primary pH buffer in the blood (keeps pH 7.35–7.45)
Transports CO₂ from tissues to lungs
Regulated by kidneys and lungs together

Magnesium

Cofactor in 300+ enzyme reactions including energy production
Relaxes smooth and skeletal muscle (counterbalances calcium)
Supports bone structure, sleep quality, and blood sugar regulation

PO₄

Phosphate

Building block of ATP — the body’s energy currency
Structural component of bones, teeth, DNA, and RNA
Part of cell membrane phospholipids

Calcium is also a critical electrolyte involved in bone structure, blood clotting, muscle contraction, and nerve function. For a detailed guide on calcium and bone markers, see our Bone Health Blood Tests page.

Electrolyte Reference Ranges

Ranges shown are based on RCPA (Royal College of Pathologists of Australasia) guidelines for adults. Your pathology report may show slightly different ranges depending on the laboratory and assay method used.

Electrolyte	Reference Range	Unit	Clinical Notes
Sodium (Na⁺)	135 – 145	mmol/L	Most abundant extracellular cation. Tightly regulated by kidneys and ADH.
Potassium (K⁺)	3.5 – 5.2	mmol/L	Primary intracellular cation. Critical for cardiac rhythm. Haemolysed samples give falsely high results.
Chloride (Cl⁻)	95 – 110	mmol/L	Major extracellular anion. Moves inversely with bicarbonate to maintain electrical neutrality.
Bicarbonate (HCO₃⁻)	22 – 32	mmol/L	Primary blood buffer. Low values suggest metabolic acidosis; high values suggest alkalosis.
Magnesium (Mg²⁺)	0.70 – 1.10	mmol/L	Cofactor in 300+ enzyme reactions. Often low in Australians, especially with PPI use.
Phosphate (PO₄³⁻)	0.75 – 1.50	mmol/L	Essential for ATP energy production, DNA/RNA, and bone mineralisation. Inverse relationship with calcium.
Calcium (corrected)	2.10 – 2.60	mmol/L	Adjusted for albumin. See bone health page for detailed calcium interpretation.
Anion Gap	8 – 16	mmol/L	Calculated: Na − Cl − HCO₃. Elevated in lactic acidosis, ketoacidosis, toxin ingestion.

Note: Potassium results can be falsely elevated if the blood sample is haemolysed (red blood cells break during collection). If your potassium is unexpectedly high, your doctor may request a repeat sample with careful venepuncture technique.

High vs Low: What Each Imbalance Means

Electrolyte imbalances range from mild (often asymptomatic) to life-threatening. The direction of the abnormality — too high or too low — determines the symptoms, causes, and urgency of treatment.

Sodium

Hypernatraemia

> 145 mmol/L

Symptoms: Intense thirst, confusion, irritability, muscle twitching, seizures in severe cases

Common causes: Dehydration (most common), diabetes insipidus, excessive salt intake, reduced water intake in elderly

Hyponatraemia

< 135 mmol/L

Symptoms: Nausea, headache, confusion, lethargy, seizures, and coma when severe (< 120)

Common causes: SIADH, thiazide diuretics, excess water intake (water intoxication), heart failure, liver cirrhosis

Potassium

Hyperkalaemia

> 5.2 mmol/L

Symptoms: Chest pain, palpitations, muscle weakness, nausea, paraesthesia (tingling)

Common causes: Kidney disease, ACE inhibitors/ARBs, potassium supplements, rhabdomyolysis, metabolic acidosis

Hypokalaemia

< 3.5 mmol/L

Symptoms: Muscle weakness, cramps, fatigue, constipation, cardiac arrhythmias

Common causes: Diuretics (thiazide, loop), vomiting, diarrhoea, excessive sweating, laxative abuse

Magnesium

Hypermagnesaemia

> 1.10 mmol/L

Symptoms: Nausea, flushing, muscle weakness, low blood pressure, bradycardia, respiratory depression

Common causes: Kidney failure (most common), excessive Mg supplements or antacids, adrenal insufficiency

Hypomagnesaemia

< 0.70 mmol/L

Symptoms: Tremor, muscle cramps, tetany, fatigue, irritability, cardiac arrhythmias

Common causes: Long-term PPI use, diuretics, alcohol use disorder, diarrhoea, coeliac disease, type 2 diabetes

Calcium

Hypercalcaemia

> 2.60 mmol/L

Symptoms: "Stones, bones, abdominal moans, psychic groans" — kidney stones, bone pain, constipation, confusion

Common causes: Primary hyperparathyroidism, malignancy, vitamin D excess, thiazide diuretics, sarcoidosis

Hypocalcaemia

< 2.10 mmol/L

Symptoms: Perioral tingling, muscle spasms (tetany), Chvostek/Trousseau signs, seizures, prolonged QT interval

Common causes: Vitamin D deficiency, hypoparathyroidism, chronic kidney disease, magnesium deficiency, pancreatitis

Medications That Affect Electrolytes

Many common medications alter electrolyte levels as a side effect. If you take any of the medications below, your doctor should monitor your electrolytes regularly. Never adjust medication doses without medical advice.

Medication Class	Effect on Electrolytes
ACE inhibitors / ARBs (e.g. ramipril, irbesartan)	↑ Potassium — reduce aldosterone-mediated K⁺ excretion
Thiazide diuretics (e.g. hydrochlorothiazide, indapamide)	↓ Potassium, ↓ Sodium, ↓ Magnesium, ↑ Calcium
Loop diuretics (e.g. frusemide, bumetanide)	↓ Potassium, ↓ Magnesium, ↓ Calcium, ↓ Sodium
PPIs (e.g. omeprazole, esomeprazole)	↓ Magnesium (long-term use > 12 months), ↓ Calcium absorption
Lithium	↑ Calcium (via PTH increase), alters sodium reabsorption (diabetes insipidus risk)
Corticosteroids (e.g. prednisolone, dexamethasone)	↓ Potassium, ↑ Sodium (mineralocorticoid effect), ↓ Calcium (long-term)
Potassium-sparing diuretics (e.g. spironolactone, amiloride)	↑ Potassium — especially dangerous combined with ACE inhibitors
Laxatives (chronic use)	↓ Potassium, ↓ Magnesium, ↓ Phosphate via GI losses

This is not a complete list. Always inform your doctor of all medications, supplements, and herbal remedies you take, as many can interact with electrolyte levels.

Who Should Have Electrolyte Testing

Electrolytes are included in most standard blood panels (EUC or CMP), so most Australians will have them checked at routine health assessments. However, more frequent monitoring is warranted in the following groups:

Routine health checks — electrolytes are part of most standard blood panels (EUC/CMP)
Patients taking diuretics, ACE inhibitors, ARBs, or other blood pressure medications
Chronic kidney disease or dialysis patients (impaired electrolyte excretion)
Heart failure patients — electrolyte shifts affect cardiac rhythm and medication safety
Persistent vomiting, diarrhoea, or nasogastric drainage (GI electrolyte losses)
Eating disorders (anorexia, bulimia) — purging causes severe electrolyte depletion
Endurance athletes — prolonged sweating depletes sodium, potassium, and magnesium
Elderly patients — reduced kidney function, polypharmacy, and impaired thirst sensation
Patients with diabetes — insulin shifts potassium, and diabetic ketoacidosis disrupts all electrolytes
Anyone experiencing unexplained muscle cramps, weakness, fatigue, or palpitations

Maintaining Healthy Electrolyte Balance

For most healthy people, a balanced diet and adequate hydration are sufficient to maintain normal electrolyte levels. These practical tips can help keep your levels in the optimal range.

Stay well hydrated — aim for 2–2.5 L of water daily (more in hot weather or exercise)

Eat potassium-rich foods — bananas, sweet potatoes, spinach, avocado, beans, and tomatoes

Include magnesium sources — dark leafy greens, nuts, seeds, whole grains, and dark chocolate

Limit processed food — packaged foods are the main source of excess sodium in Australian diets

Moderate salt intake — aim for < 6 g salt (< 2,300 mg sodium) per day

Don’t over-hydrate — excessive water without electrolytes can cause dangerous hyponatraemia

Consider oral rehydration salts during illness with vomiting or diarrhoea

Discuss magnesium supplementation with your GP if taking long-term PPIs

Eat calcium-rich foods daily — dairy, sardines, tofu, fortified plant milks

Have electrolytes checked regularly if on diuretics or blood pressure medications

Related Blood Test Guides

Kidney Function

The kidneys are the primary regulators of electrolyte balance — kidney disease is the most common cause of electrolyte disturbances.

Bone Health

Calcium, phosphate, and magnesium are essential bone minerals. Detailed calcium and vitamin D interpretation.

Cardiac Biomarkers

Electrolyte imbalances directly affect heart rhythm. Potassium and magnesium are critical for cardiac function.

Nutritional Deficiencies

Magnesium, phosphate, and calcium deficiencies often accompany vitamin and mineral deficiencies.

Blood Test Preparation

How to prepare for blood tests to ensure accurate electrolyte results, including fasting and hydration.

Headaches & Migraines

Electrolyte imbalances — especially magnesium and sodium — are common triggers for headaches.

Seek urgent medical attention if you experience any of the following:

• Severe potassium abnormality — potassium < 2.5 or > 6.0 mmol/L is a medical emergency (risk of cardiac arrest)
• Severe sodium abnormality — sodium < 120 or > 155 mmol/L requires urgent hospital management
• Confusion or altered consciousness with known electrolyte imbalance — may indicate cerebral oedema
• Irregular heartbeat (palpitations, skipped beats) with muscle weakness — suggests potassium or magnesium disturbance
• Seizures or muscle tetany — can occur with severe calcium, sodium, or magnesium derangement
• Persistent vomiting or diarrhoea lasting more than 24 hours — risk of dangerous dehydration and electrolyte depletion

Track Your Electrolytes Over Time

Upload your blood test results and watch your sodium, potassium, magnesium, and other electrolyte levels trend on interactive charts. Spot patterns, track the impact of medication changes, and share reports with your doctor — free forever for the first million users.

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Medical Disclaimer: This guide is for educational purposes only and does not constitute medical advice. Electrolyte results must be interpreted by a qualified healthcare professional in the context of your medications, kidney function, hydration status, and clinical history. Never adjust medication doses or start supplements based on information found online. Reference ranges are based on RCPA guidelines and may vary between laboratories.