Electrolytes are minerals that carry an electric charge when dissolved in your body’s fluids. The seven main electrolytes in your body are sodium, potassium, calcium, magnesium, chloride, bicarbonate, and phosphate. They’re present in your blood, tissues, and urine, and they control everything from your heartbeat to the way your muscles contract to how much water your cells hold.
The Seven Major Electrolytes
Sodium is the dominant electrolyte outside your cells. It controls how much fluid your body retains and plays a direct role in nerve signaling and muscle function. Your blood sodium normally sits between 135 and 145 milliequivalents per liter.
Potassium is sodium’s counterpart, concentrated inside your cells. It keeps your heart, muscles, and cells working properly. Normal blood potassium ranges from 3.5 to 5 mEq/L, a narrow window that your body works hard to maintain.
Calcium does far more than build bones. It’s essential for muscle contraction, nerve impulse transmission, blood clotting, and hormone secretion. Normal blood calcium runs between 8.5 and 10.3 mg/dL, with about 99% of your total calcium stored in bones and teeth.
Magnesium supports muscle and nerve function, helps regulate blood pressure, and plays a role in blood sugar control. Normal levels range from 1.5 to 2.4 mEq/L.
Chloride works alongside sodium to manage fluid balance, blood volume, and blood pressure.
Bicarbonate is your body’s primary pH buffer, keeping blood from becoming too acidic or too alkaline. It also shuttles carbon dioxide through your bloodstream to your lungs for exhaling. Normal levels fall between 22 and 26 mEq/L.
Phosphate partners with calcium to strengthen bones and teeth, and it participates in energy production at the cellular level.
How Electrolytes Power Your Nerves and Muscles
The reason electrolytes matter so much comes down to electricity. Your nerve and muscle cells communicate through rapid shifts in electrical charge across their membranes, and those shifts depend entirely on the movement of charged ions.
At rest, your cells maintain a higher concentration of potassium inside and sodium outside. When a nerve needs to fire, tiny channels in the cell membrane snap open and let sodium rush in. This flood of positive charge triggers what’s called an action potential, a rapid spike in voltage that travels down the nerve like a signal through a wire. Milliseconds later, potassium channels open and potassium flows out, resetting the voltage. A pump on the cell membrane then moves three sodium ions back out for every two potassium ions it pulls in, restoring the original balance. This cycle repeats every time you think, move, or feel.
Your heart uses a variation of the same system. Pacemaker cells in the heart generate their own rhythmic electrical impulses, but instead of relying primarily on sodium, they use calcium flowing through specialized channels to trigger each beat. That’s why both calcium and potassium imbalances can cause dangerous heart rhythm problems.
Fluid Balance and Blood pH
Sodium is the main driver of fluid balance. Water follows sodium, so wherever sodium concentrations are higher, water moves in that direction. Your kidneys regulate how much sodium you retain or excrete, which in turn controls your blood volume and blood pressure. Potassium works in opposition, helping your body release excess sodium through urine.
Bicarbonate handles acid-base balance. Carbon dioxide produced by your cells combines with water to form carbonic acid, which then splits into bicarbonate and a hydrogen ion. This buffering reaction prevents your blood pH from shifting dangerously. Your kidneys fine-tune bicarbonate levels, while your lungs control how much carbon dioxide you breathe out. Phosphate acts as a secondary buffer, particularly important for regulating urine pH.
What Causes Electrolyte Imbalances
The most common causes are dehydration, prolonged vomiting or diarrhea, heavy sweating, and certain medications. Diuretics, which are widely prescribed for high blood pressure and heart failure, are among the biggest culprits. Loop diuretics (like furosemide) tend to cause low potassium and, paradoxically, high sodium because they cause you to lose proportionally more water than salt. Thiazide diuretics are associated with low sodium and low potassium. Aldosterone-blocking diuretics can cause the opposite pattern: low sodium and high potassium.
Kidney disease, hormonal disorders, and eating disorders also frequently disrupt electrolyte levels, since the kidneys are the primary regulators of electrolyte concentrations in the blood.
Symptoms of an Imbalance
Mild electrolyte imbalances often produce vague symptoms: fatigue, muscle cramps, headaches, or irritability. As imbalances worsen, the symptoms become more specific and more serious.
- Low sodium causes nausea, confusion, and in severe cases, seizures. Sodium below 135 mmol/L is considered hyponatremia, and it can cause brain cells to swell as water shifts into them.
- Low potassium leads to muscle weakness, cramping, and irregular heartbeats. Severe depletion can cause life-threatening cardiac arrhythmias.
- Low calcium produces tingling in the fingers and around the mouth, muscle spasms, and in extreme cases, seizures.
- Low magnesium often accompanies low potassium and low calcium, amplifying symptoms like muscle twitching, tremors, and heart rhythm disturbances.
High levels of these electrolytes carry their own risks. Elevated potassium is particularly dangerous because it can slow or stop the heart without much warning.
Electrolytes and Exercise
When you sweat, you lose electrolytes, primarily sodium and chloride. Sodium concentration in sweat varies enormously between individuals, ranging from about 10 to 70 millimoles per liter across the whole body. The harder you work and the more you sweat, the more sodium you lose per liter, because your sweat glands can’t reabsorb sodium fast enough at high output rates.
For moderate exercise lasting under an hour, water alone is typically sufficient. During prolonged or intense activity, replacing sodium becomes important. Drinking excessive plain water without replacing sodium can actually dilute your blood sodium to dangerous levels. This condition, called exercise-associated hyponatremia, was first documented in marathon runners in 1985 and remains a real risk during endurance events. It occurs when total body water overwhelms the available sodium, causing cells to swell. Symptoms range from nausea and confusion to seizures.
Food Sources of Key Electrolytes
Most people get adequate electrolytes from a varied diet without needing supplements or sports drinks. The major dietary sources break down predictably by mineral.
For potassium, fruits, vegetables, and legumes provide the largest share, about 26% of typical intake. Potatoes, dairy products, meat, and coffee contribute meaningful amounts as well. For calcium, cheese alone accounts for nearly 30% of average intake, with other dairy products adding another 20%. Mineral water and unsweetened tea supply about 12.5%. Magnesium comes from a broader mix: fruits, vegetables, legumes, whole grain bread, coffee, tea, and mineral water all contribute between 6 and 15% each.
Sodium is rarely a concern for deficiency in typical diets. Most people consume well above what they need through processed foods, restaurant meals, and added table salt. The greater dietary challenge for most adults is getting enough potassium and magnesium, which depend on consistent intake of produce, whole grains, nuts, and seeds.