Medication Administration Routes: PO, SQ,

Medication Administration Routes: PO, SQ, IM, and IV Principles

By Nurse Jude · Updated June 18, 2026

A concise study guide on the four primary medication administration routes — oral, subcutaneous, intramuscular, and intravenous — covering technique, sites, volumes, and common exam traps.

Safe medication administration depends on choosing the correct route and applying route-specific technique. This note reviews the four primary routes — oral (PO), subcutaneous (SQ), intramuscular (IM), and intravenous (IV) — with key rules, sites, volumes, and common exam pitfalls.

Routes Overview

Route	Key Use	Onset Speed
Oral (PO)	Systemic effect	Slow
Subcutaneous (SQ)	Insulin, heparin	Moderate
Intramuscular (IM)	Vaccines, medications	Fast
Intravenous (IV)	Immediate effect	Fastest

Depth, Angle, and Volume

Route	Needle Angle	Max Volume
Oral	N/A	N/A
Subcutaneous	45°–90°	≤ 1 mL
Intramuscular	90°	2–3 mL
Intravenous	0° (parallel to vein)	Continuous

Oral (PO) Administration

Position patient upright before administration.
Assess swallowing ability prior to giving the medication.
Give with water unless contraindicated.
Never crush enteric-coated or extended-release medications.
Do not give oral medications to unconscious patients.

Subcutaneous (SQ) Administration

Used primarily for insulin and heparin.
Preferred site: abdomen.
Rotate injection sites to prevent tissue damage.
Pinch the skin fold before injecting.
Do not aspirate.

Intramuscular (IM) Administration

Insert needle at a 90-degree angle.
Preferred site: ventrogluteal.
Use the deltoid for small volumes.
Avoid the dorsogluteal site due to risk of sciatic nerve injury.
Follow facility policy on aspiration.

Intravenous (IV) Administration

Fastest route — and the highest risk.
Verify IV patency before giving medication.
Assess the IV site frequently for signs of complications.
Never IV push potassium.
Stop the infusion immediately if infiltration occurs.

Common Route-Specific Exam Traps

Crushing extended-release oral medications.
Injecting insulin IM instead of SQ.
Using the dorsogluteal site for IM injections.
Rapid IV push without an order.

Key Takeaways

IV = fastest onset, highest risk; always verify patency and never IV push potassium.
IM = 90° angle, ventrogluteal preferred, avoid dorsogluteal.
SQ = 45°–90°, ≤ 1 mL, used for insulin and heparin; do not aspirate.
PO requires intact swallowing and an upright position — never give to unconscious patients.
Never crush enteric-coated or extended-release tablets.
Wrong route = medication error.