An Electrolytes Panel (Serum)—sometimes called electrolytes, lytes, Chem-4, or part of a basic metabolic panel—measures key minerals in your blood that help control fluid balance, nerve and muscle function, and the body’s acid–base (pH) balance. This panel typically includes sodium, potassium, chloride, and bicarbonate (often reported as CO₂ or “total CO₂”).

These electrolytes work together to keep cells functioning properly:

Sodium (Na) helps regulate how much water is in and around your cells and supports blood pressure and nerve signaling. Too high or too low sodium can cause symptoms such as confusion, headaches, weakness, or, in severe cases, seizures.

Potassium (K) is essential for normal heart rhythm and muscle function. Abnormal potassium (high or low) can lead to muscle cramps or weakness, tingling, or dangerous heart rhythm changes.

Chloride (Cl) helps maintain fluid balance and works with sodium and bicarbonate to keep acid–base levels steady. Chloride changes often mirror changes in sodium and hydration status.

Bicarbonate (HCO₃⁻ / CO₂) reflects your body’s buffering system that keeps your blood pH in a safe range. Low bicarbonate may suggest metabolic acidosis (too much acid or too little base), while high bicarbonate may suggest metabolic alkalosis (too much base or loss of acid), though interpretation depends on your symptoms and other labs.

Results are interpreted together rather than one number at a time. Patterns can point to issues such as dehydration or overhydration, kidney function problems, medication effects (for example, diuretics), or acid–base disturbances from vomiting, diarrhea, lung disease, or uncontrolled diabetes. Your clinician will interpret the results based on your age, medical history, current symptoms, and any other tests ordered.

Doctors commonly order a serum electrolytes panel to check hydration status and to evaluate how well the kidneys and the body’s acid–base system are working. It is frequently used in routine care and urgent settings because electrolyte imbalances can become serious if not treated.

This test may be ordered if you have symptoms that could be related to electrolyte or fluid imbalance, such as:

Weakness, fatigue, muscle cramps, twitching, or numbness/tingling; nausea or vomiting; diarrhea; excessive thirst; swelling (edema); dizziness or fainting; confusion, irritability, or severe headache; irregular heartbeat, palpitations, or chest discomfort; or shortness of breath in the context of acid–base concerns.

It’s also commonly ordered to monitor or evaluate:

Dehydration (from illness, heat exposure, poor intake) or overhydration; kidney disease or suspected kidney injury; heart failure or fluid management; uncontrolled diabetes and possible ketoacidosis; suspected acid–base disorders (for example, after prolonged vomiting, severe diarrhea, or certain lung conditions); and medication effects such as from diuretics (“water pills”), ACE inhibitors/ARBs, certain blood pressure medicines, steroids, laxative overuse, or lithium.

It may be used before surgery or during hospitalization, as well as for ongoing monitoring in people with chronic conditions. In emergency care, electrolytes are often checked when someone is very ill, dehydrated, has altered mental status, or has heart rhythm concerns.

• Dehydration and volume depletion
• Overhydration / water intoxication (hyponatremia)
• Chronic kidney disease (CKD) and acute kidney injury (AKI)
• Heart failure and fluid overload states
• Hyponatremia or hypernatremia (abnormal sodium levels)
• Hypokalemia or hyperkalemia (abnormal potassium levels)
• Metabolic acidosis (including diabetic ketoacidosis)
• Metabolic alkalosis (often related to vomiting or diuretic use)
• Gastrointestinal losses (prolonged vomiting or diarrhea)
• Adrenal disorders (e.g., Addison’s disease)

• Monitoring hydration and electrolyte balance during illness, heat exposure, or athletic training
• Supporting kidney health monitoring (especially if you have CKD risk factors)
• Medication safety monitoring (e.g., diuretics, blood pressure medicines, lithium)
• Tracking heart rhythm–related risk by keeping potassium and other electrolytes in a safe range
• Evaluating and monitoring acid–base (pH) balance in complex medical conditions
• General wellness screening as part of routine bloodwork (often alongside other chemistry tests)