NHA PHLEBOTOMY EXAM QUESTIONS
NHA PHLEBOTOMY EXAM QUESTIONS AND
CORRECT DETAILED ANSWERS ALREADY
GRADED A 2026-2027., Exams of Clinical
Medicine
Order of Draw & Tube Additives
Which is the correct order of draw when collecting multiple tubes during
venipuncture?
A. Lavender, red, light blue, gold
B. Light blue, gold/red, green, lavender, gray
C. Gray, green, gold, lavender, light blue
D. Gold, light blue, green, gray, lavender
Answer: B. The standardized CLSI order of draw is: blood culture bottles/tubes
first, then light blue (sodium citrate), gold/red (serum, with or without gel
separator), green (heparin), lavender (EDTA), and gray (fluoride/oxalate) last. This
sequence prevents additive carryover from one tube contaminating the next,
which could alter test results, especially important because even trace amounts of
certain additives like EDTA can interfere with coagulation studies or electrolyte
panels.
What is the additive found in a lavender-top tube, and what is its primary
purpose?
A. Sodium citrate; used for coagulation studies
B. EDTA; used to prevent clotting for CBC and other hematology tests
C. Clot activator; used for serum chemistry tests
D. Sodium fluoride; used for glucose testing
Answer: B. EDTA works by binding calcium, which is essential for the clotting
cascade, effectively preventing coagulation while preserving cell morphology,
making lavender tubes the standard choice for complete blood counts and other
hematology testing.
Page 1 of 28
, NHA PHLEBOTOMY EXAM QUESTIONS
A light blue-top tube is used for which type of testing, and why is proper fill
volume critical?
A. Chemistry testing; fill volume doesn't matter
B. Coagulation studies (like PT/INR); proper fill volume ensures the correct blood-
to-citrate ratio
C. Blood typing; any fill volume is acceptable
D. Glucose testing; fill volume affects color only
Answer: B. Light blue tubes contain sodium citrate in a precise ratio with blood
(typically 9:1) to allow accurate coagulation testing. An underfilled tube changes
this ratio, causing falsely prolonged clotting times, so these tubes must be filled to
the exact indicated volume for valid results.
Why must a gray-top tube be used for glucose testing rather than a serum tube
alone?
A. Gray tubes contain an anticoagulant only
B. Gray tubes contain sodium fluoride, which inhibits glycolysis and preserves
glucose levels
C. Gray tubes have no additive
D. Gray tubes are only used for coagulation testing
Answer: B. Red blood cells continue to metabolize glucose through glycolysis after
collection, causing falsely low glucose readings over time if left in a plain tube.
Sodium fluoride in gray-top tubes inhibits this enzymatic process, preserving
accurate glucose concentrations even if testing is delayed.
Venipuncture Technique & Site Selection
Which vein is the first choice for venipuncture in most adult patients?
A. Basilic vein
B. Median cubital vein
C. Cephalic vein
D. Femoral vein
Answer: B. The median cubital vein is typically the largest, most stable, and least
painful site for venipuncture, and it lies further from major nerves and arteries
Page 2 of 28
, NHA PHLEBOTOMY EXAM QUESTIONS
compared to other antecubital veins, making it the safest and most preferred first
choice.
Why should the basilic vein be used with extra caution during venipuncture?
A. It is too small to access
B. It lies close to the brachial artery and median nerve, increasing risk of injury
C. It is located only in pediatric patients
D. It cannot be used for blood collection at all
Answer: B. The basilic vein runs in close proximity to the brachial artery and
median nerve on the medial side of the antecubital area, so improper technique
increases the risk of arterial puncture or nerve damage, making careful site
selection and technique especially important here.
A patient has a fistula in the left arm for dialysis access. What should the
phlebotomist do?
A. Draw blood from the fistula arm as usual
B. Avoid the fistula arm entirely and select an alternate site
C. Apply the tourniquet directly over the fistula
D. Use only a butterfly needle on the fistula
Answer: B. Venipuncture should never be performed on an arm with a fistula,
graft, or on the same side as a mastectomy with lymph node removal, as this can
damage the access site, impair its function, or increase complication risk. An
alternate limb should always be used.
How long should a tourniquet remain applied before it should be released or
reapplied?
A. No more than 1 minute
B. No longer than 1 minute, ideally released once blood flow begins
C. Up to 5 minutes is acceptable
D. Tourniquet time has no effect on results
Answer: B. Prolonged tourniquet application (over 1 minute) can cause
hemoconcentration, where fluid shifts out of the vessel and concentrates cellular
elements and larger molecules, potentially skewing results for tests like
potassium, protein, and cell counts.
Page 3 of 28
NHA PHLEBOTOMY EXAM QUESTIONS AND
CORRECT DETAILED ANSWERS ALREADY
GRADED A 2026-2027., Exams of Clinical
Medicine
Order of Draw & Tube Additives
Which is the correct order of draw when collecting multiple tubes during
venipuncture?
A. Lavender, red, light blue, gold
B. Light blue, gold/red, green, lavender, gray
C. Gray, green, gold, lavender, light blue
D. Gold, light blue, green, gray, lavender
Answer: B. The standardized CLSI order of draw is: blood culture bottles/tubes
first, then light blue (sodium citrate), gold/red (serum, with or without gel
separator), green (heparin), lavender (EDTA), and gray (fluoride/oxalate) last. This
sequence prevents additive carryover from one tube contaminating the next,
which could alter test results, especially important because even trace amounts of
certain additives like EDTA can interfere with coagulation studies or electrolyte
panels.
What is the additive found in a lavender-top tube, and what is its primary
purpose?
A. Sodium citrate; used for coagulation studies
B. EDTA; used to prevent clotting for CBC and other hematology tests
C. Clot activator; used for serum chemistry tests
D. Sodium fluoride; used for glucose testing
Answer: B. EDTA works by binding calcium, which is essential for the clotting
cascade, effectively preventing coagulation while preserving cell morphology,
making lavender tubes the standard choice for complete blood counts and other
hematology testing.
Page 1 of 28
, NHA PHLEBOTOMY EXAM QUESTIONS
A light blue-top tube is used for which type of testing, and why is proper fill
volume critical?
A. Chemistry testing; fill volume doesn't matter
B. Coagulation studies (like PT/INR); proper fill volume ensures the correct blood-
to-citrate ratio
C. Blood typing; any fill volume is acceptable
D. Glucose testing; fill volume affects color only
Answer: B. Light blue tubes contain sodium citrate in a precise ratio with blood
(typically 9:1) to allow accurate coagulation testing. An underfilled tube changes
this ratio, causing falsely prolonged clotting times, so these tubes must be filled to
the exact indicated volume for valid results.
Why must a gray-top tube be used for glucose testing rather than a serum tube
alone?
A. Gray tubes contain an anticoagulant only
B. Gray tubes contain sodium fluoride, which inhibits glycolysis and preserves
glucose levels
C. Gray tubes have no additive
D. Gray tubes are only used for coagulation testing
Answer: B. Red blood cells continue to metabolize glucose through glycolysis after
collection, causing falsely low glucose readings over time if left in a plain tube.
Sodium fluoride in gray-top tubes inhibits this enzymatic process, preserving
accurate glucose concentrations even if testing is delayed.
Venipuncture Technique & Site Selection
Which vein is the first choice for venipuncture in most adult patients?
A. Basilic vein
B. Median cubital vein
C. Cephalic vein
D. Femoral vein
Answer: B. The median cubital vein is typically the largest, most stable, and least
painful site for venipuncture, and it lies further from major nerves and arteries
Page 2 of 28
, NHA PHLEBOTOMY EXAM QUESTIONS
compared to other antecubital veins, making it the safest and most preferred first
choice.
Why should the basilic vein be used with extra caution during venipuncture?
A. It is too small to access
B. It lies close to the brachial artery and median nerve, increasing risk of injury
C. It is located only in pediatric patients
D. It cannot be used for blood collection at all
Answer: B. The basilic vein runs in close proximity to the brachial artery and
median nerve on the medial side of the antecubital area, so improper technique
increases the risk of arterial puncture or nerve damage, making careful site
selection and technique especially important here.
A patient has a fistula in the left arm for dialysis access. What should the
phlebotomist do?
A. Draw blood from the fistula arm as usual
B. Avoid the fistula arm entirely and select an alternate site
C. Apply the tourniquet directly over the fistula
D. Use only a butterfly needle on the fistula
Answer: B. Venipuncture should never be performed on an arm with a fistula,
graft, or on the same side as a mastectomy with lymph node removal, as this can
damage the access site, impair its function, or increase complication risk. An
alternate limb should always be used.
How long should a tourniquet remain applied before it should be released or
reapplied?
A. No more than 1 minute
B. No longer than 1 minute, ideally released once blood flow begins
C. Up to 5 minutes is acceptable
D. Tourniquet time has no effect on results
Answer: B. Prolonged tourniquet application (over 1 minute) can cause
hemoconcentration, where fluid shifts out of the vessel and concentrates cellular
elements and larger molecules, potentially skewing results for tests like
potassium, protein, and cell counts.
Page 3 of 28
