Lesson · 26 min

Venipuncture Technique

Collect blood safely: site selection, the order of draw, and the errors that compromise a specimen or harm a patient.

By the end of this lesson you can

Select an appropriate venipuncture site
State the order of draw and explain why it exists
Identify errors causing hemolysis or contamination
Respond to complications during a draw

📘 Reading Lesson

Lesson Notes

Read through the key concepts before you try the challenge.

Site selection first

On the job

You draw blood at Lakeside Medical Associates.

A patient has had a mastectomy with lymph node removal on the left, and an IV running in the right forearm. Both arms have constraints, and choosing wrongly risks lymphedema on one side or a diluted specimen on the other. The decision happens before the needle comes out of the packet.

Your task: Learn site selection and the order of draw, which together determine whether the specimen is usable.

The antecubital fossa is the standard site. The median cubital vein is the first choice — it is generally the largest, best anchored, and furthest from the brachial artery and median nerve. The cephalic vein is the second choice, and the basilic vein the last, because it sits close to the brachial artery and median nerve.

Avoid	Why
The arm on the side of a mastectomy with node removal	Risk of lymphedema; use the other arm or consult the provider
An arm with an IV running	The specimen may be diluted with IV fluid
An arm with a dialysis fistula or graft	Never — risk to vascular access
Areas with hematoma, scarring, or burns	Painful, and results may be inaccurate
Feet and ankles	Higher risk of thrombosis; generally requires provider authorization
Directly over the basilic vein where avoidable	Proximity to the brachial artery and median nerve

Sites and situations to avoid

#	Tube	Additive	Why this position
1	Blood culture bottle	Sterile	Drawn first to prevent contamination
2	Light blue	Sodium citrate	Coagulation testing needs an exact blood-to-additive ratio
3	Red or gold/SST	Clot activator, gel	Before additive tubes that could carry over
4	Green	Heparin	Carryover would affect later tubes
5	Lavender or pink	EDTA	EDTA carryover badly distorts chemistry results
6	Gray	Sodium fluoride/oxalate	Last — its additives interfere with most other tests

Order of draw (CLSI)

The order of draw exists to prevent additive carryover between tubes. Drawing out of order can produce results that are wrong but entirely plausible — EDTA carryover into a chemistry tube falsely elevates potassium and falsely lowers calcium, and nothing about the result looks anomalous. A patient can be treated for a condition they do not have on the strength of a tube drawn in the wrong sequence.

Error	Causes
Tourniquet left on over one minute	Hemoconcentration; falsely elevated results
Vigorous shaking of tubes	Hemolysis; falsely elevated potassium
Needle too small for the draw	Hemolysis from shear stress
Underfilled light blue tube	Wrong blood-to-citrate ratio; coagulation results invalid
Alcohol not dry before puncture	Stinging, and possible specimen contamination
Probing or redirecting the needle blindly	Nerve injury, arterial puncture, hematoma

Errors and their consequences

Two hard limits. Never make more than two attempts on one patient — pass them to a colleague, which is standard practice rather than a failure. And if a patient reports sharp, shooting, or electric pain, or numbness or tingling radiating down the arm, remove the needle immediately: those are signs of nerve involvement, and continuing risks lasting injury. Never probe laterally with the needle in the arm.

Check your understanding

Why must a light blue sodium citrate tube be filled completely?

Challenge

Apply what you've learned in this lesson.

Venipuncture is a hands-on skill requiring supervised practice on manikins before patients. This is the knowledge that must precede it.

Write the order of draw from memory with the additive in each tube, then check against a CLSI reference.
For each situation, state which arm you would use and why: mastectomy left with node removal; IV in the right forearm; dialysis fistula in the left arm; hematoma in the right antecubital fossa.
Research hemolysis. List five causes and the specific test results each distorts.
Write out what you would say and do if a patient reported shooting pain down the arm mid-draw.

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Specimen Handling and Point-of-Care Testing →