Sodium (Na+) regulates fluid balance, blood volume, and nerve function.
NORMAL RANGE: 135-145 mEq/L
Hyponatremia (below 135 mEq/L):

• SIGNS: confusion, seizures, muscle cramps.
  Hypernatremia (above 145 mEq/L):
• SIGNS: thirst, seizures, confusion, muscle twitching.

Potassium (K+) regulates muscle and nerve function, especially the heart.
NORMAL RANGE: 3.5-5.0 mEq/L
Hypokalemia (below 3.5 mEq/L):

• SIGNS: irregular heart rhythm, cramps, muscle weakness.
  Hyperkalemia (above 5.0 mEq/L):
• SIGNS: weakness, heart arrhythmias, cardiac arrest.

Calcium (Ca2+) is crucial for bone and teeth health as well as muscle function.
NORMAL RANGE: 8.5-10.5 mg/dL
Hypocalcemia (below 8.5 mg/dL):

• SIGNS: Trousseau's sign, Chvostek's sign, muscle cramps, weakness.
  Hypercalcemia (above 10.5 mg/dL):
• SIGNS: fractures, arrhythmias, constipation, confusion.

Magnesium (Mg2+) is involved in muscle and nerve function.
NORMAL RANGE: 1.5-2.5 mEq/L
Hypomagnesemia (below 1.5 mEq/L):

• SIGNS: muscle cramps, tremors, seizures, "Torsades de Pointes."
  Hypermagnesemia (above 2.5 mEq/L):
• SIGNS: depressed deep tendon reflexes, drowsiness, low blood pressure.

Chloride (Cl-) helps maintain fluid balance.
NORMAL RANGE: 98-106 mEq/L
Hypochloremia (below 98 mEq/L):

• SIGNS: tetany, muscle cramps, seizures, dehydration.
  Hyperchloremia (above 106 mEq/L):
• SIGNS: tachypnea, low heart rate, weakness.

Phosphate supports bone health and ATP production.
NORMAL RANGE: 2.5-4.5 mEq/L
Hypophosphatemia (below 2.5 mEq/L):

• SIGNS: dysphagia, bone pain, confusion, seizures.
  Hyperphosphatemia (above 4.5 mEq/L):
• SIGNS: muscle cramps, anorexia, hyperreflexia.