ORIGINAL STUDY GUIDE
Fluids & Electrolytes
A Clear, Systematic Nursing Review
Concept review + original practice questions with rationales
For nursing students — not affiliated with NCLEX®, ATI®, or HESI®
, About this guide. This is original educational material written to help you learn core nursing concepts. All practice
questions were written from scratch for this guide. It is a study aid, not real or recalled exam content, and is not affiliated
with or endorsed by any testing organization.
Why This Topic Trips People Up
Fluid and electrolyte questions test whether you can connect a lab value to what you would actually see and
do at the bedside. The trick is to learn the normal ranges cold, then memorize the signs of both high and low
for each electrolyte, and finally the priority nursing action. This guide walks that path.
Normal Ranges to Memorize
Electrolyte / value Normal range
Sodium (Na+) 135–145 mEq/L
Potassium (K+) 3.5–5.0 mEq/L
Calcium (Ca2+) 9.0–10.5 mg/dL
Magnesium (Mg2+) 1.5–2.5 mEq/L
Chloride (Cl-) 97–107 mEq/L
Phosphorus 3.0–4.5 mg/dL
Tip: potassium has the tightest range and the most dangerous consequences — both highs and lows can be
fatal through cardiac effects. Prioritize it.
Potassium: The One to Know Best
Hypokalemia (K+ < 3.5)
• Causes: diuretics (loop/thiazide), vomiting, diarrhea, NG suction.
• Signs: muscle weakness, leg cramps, decreased bowel sounds, flat/inverted T waves, U waves on ECG.
• Action: replace K+. Never give IV potassium by IV push — always dilute and infuse slowly.
Hyperkalemia (K+ > 5.0)
• Causes: renal failure, K+-sparing diuretics, crush injuries, acidosis.
• Signs: muscle weakness, peaked T waves, wide QRS, cardiac arrest risk.
• Action: recognize ECG changes as priority. Treatments include calcium gluconate (cardiac protection),
insulin + glucose, and potassium binders.
Sodium & Fluid Volume
Hyponatremia (Na < 135) — confusion, seizures, headache. Often dilutional. Restrict fluids as ordered.
Hypernatremia (Na > 145) — thirst, dry mucous membranes, restlessness. Encourage/administer fluids as
ordered.
Fluid Volume Deficit vs. Overload
Fluid Volume Deficit Fluid Volume Overload
Tachycardia, weak pulse Bounding pulse
Fluids & Electrolytes
A Clear, Systematic Nursing Review
Concept review + original practice questions with rationales
For nursing students — not affiliated with NCLEX®, ATI®, or HESI®
, About this guide. This is original educational material written to help you learn core nursing concepts. All practice
questions were written from scratch for this guide. It is a study aid, not real or recalled exam content, and is not affiliated
with or endorsed by any testing organization.
Why This Topic Trips People Up
Fluid and electrolyte questions test whether you can connect a lab value to what you would actually see and
do at the bedside. The trick is to learn the normal ranges cold, then memorize the signs of both high and low
for each electrolyte, and finally the priority nursing action. This guide walks that path.
Normal Ranges to Memorize
Electrolyte / value Normal range
Sodium (Na+) 135–145 mEq/L
Potassium (K+) 3.5–5.0 mEq/L
Calcium (Ca2+) 9.0–10.5 mg/dL
Magnesium (Mg2+) 1.5–2.5 mEq/L
Chloride (Cl-) 97–107 mEq/L
Phosphorus 3.0–4.5 mg/dL
Tip: potassium has the tightest range and the most dangerous consequences — both highs and lows can be
fatal through cardiac effects. Prioritize it.
Potassium: The One to Know Best
Hypokalemia (K+ < 3.5)
• Causes: diuretics (loop/thiazide), vomiting, diarrhea, NG suction.
• Signs: muscle weakness, leg cramps, decreased bowel sounds, flat/inverted T waves, U waves on ECG.
• Action: replace K+. Never give IV potassium by IV push — always dilute and infuse slowly.
Hyperkalemia (K+ > 5.0)
• Causes: renal failure, K+-sparing diuretics, crush injuries, acidosis.
• Signs: muscle weakness, peaked T waves, wide QRS, cardiac arrest risk.
• Action: recognize ECG changes as priority. Treatments include calcium gluconate (cardiac protection),
insulin + glucose, and potassium binders.
Sodium & Fluid Volume
Hyponatremia (Na < 135) — confusion, seizures, headache. Often dilutional. Restrict fluids as ordered.
Hypernatremia (Na > 145) — thirst, dry mucous membranes, restlessness. Encourage/administer fluids as
ordered.
Fluid Volume Deficit vs. Overload
Fluid Volume Deficit Fluid Volume Overload
Tachycardia, weak pulse Bounding pulse
