Medical Assistant’s Guide to
Venipuncture (Phlebotomy)

Many of today’s large medical practices have in-office laboratories. Offering diagnostic services on-site is cost effective, convenient for the patient, and it makes the most of health care resources.

But when the doctor orders a blood test, it takes skilled staff to draw a sample. Called venipuncture or phlebotomy, it’s one of a medical assistant’s most valuable skills.

What Is Venipuncture?

Venipuncture—“veni,” meaning vein, and “puncture,” meaning to pierce—is the act of drawing blood from a vein with a needle. It’s a minimally invasive way to collect blood cells and plasma, the liquid component of blood, for analysis.

In most circles, the terms venipuncture and phlebotomy are used interchangeably.

Arterial sticks, blood drawn from arteries, as well as samples taken from central catheters, are more complex procedures performed only by trained registered nurses or respiratory therapists. Arterial blood is used only to check body pH and blood gasses, oxygen, and carbon dioxide, so the vast majority of blood samples come from veins.

How Are Venous Blood Samples Used?

The chemical substances in blood reflect what’s happening in the body. When a specific component isn’t in a normal range, it could indicate a problem. In practice, doctors use blood tests for these purposes.

  • Assess general health
  • Determine blood type
  • Diagnose disease
  • Monitor the therapeutic effects of high-risk medications, such as anticoagulants
  • Identify risk factors for chronic conditions, such as heart disease

Biochemical analysis of blood can detect a wide range of conditions.

  • Cancer
  • Diabetes
  • Anemia
  • Lyme disease
  • Rheumatoid arthritis
  • High cholesterol
  • Hyperthyroidism
  • Infections
  • Vitamin and mineral deficiencies
  • Kidney and liver diseases

The Medical Assistant’s Role

For a medical assistant with both clinical and administrative training, venipuncture is a perfect task. It’s both an art and a science, requiring technical and clerical expertise, as well as sound clinical judgment.

Steps in the process include reviewing the doctor’s order, screening the patient, obtaining consent, gathering equipment, and then performing the venipuncture.

Review the Doctor’s Order

Doctors order blood tests with a purpose. Screening tests done during a patient’s annual exam, for example, help the doctor identify health risks such as high cholesterol, but most tests are ordered in response to a physical complaint or symptom.

In addition to reviewing lab orders for completeness and accuracy, medical assistants also code requisition forms. These documents tell the laboratory which tests to do and how to bill the insurer via an ICD-10 code that corresponds with the test’s purpose. Insurance companies have strict criteria for which tests they will pay for and why, so miscoding a requisition can result in claim denial and an unexpected bill for the patient.

It’s also vital for medical assistants to understand why a test was ordered because it can impact instructions for patient preparation. In some cases, it also affects how to do tests and how to report results.

Screen the Patient

A significant number of common blood tests require patients to prepare in advance, usually by fasting for 8, 10, or 12 hours. Cholesterol, triglyceride, and blood glucose testing fall into this group. Failure to fast could result in artificially high results and lead to unnecessary treatments. Before doing a venipuncture, medical assistants should verify that patients followed all instructions.

Patients should then be screened for reactions when blood is drawn. Anxious patients could faint, so they must be sitting or lying in a safe position when the sample is taken. Having an extra staff member in the room to distract a nervous child is always helpful.

Finally, when the venipuncture is complete, a small adhesive bandage is applied to the wound to prevent blood from seeping into patients’ clothing. Checking for allergies to adhesives or the cleansing agents used to prepare before venipuncture is essential.

Obtain Consent

It’s a patient’s right to know why a blood test was ordered and how it will be performed. Before proceeding with venipuncture, medical assistants should explain the procedure and its purpose and obtain consent, if required.

If the patient is a minor, consent comes from the parent or legal guardian. Pre-procedure is also the ideal time to review when patients can expect results and how they will be delivered. Medical assistants should also verify who can legally receive them under patient privacy guidelines.

Gather Equipment

The venipuncture process is standardized to ensure consistent results. Mishandled or mislabeled samples may be rejected by laboratories. The equipment that processes blood is carefully calibrated. Following the rules is the best way to avoid redraws.

Before the procedure, medical assistants should gather all the necessary supplies, including personal protective equipment, cleansing pads, needles, blood collection tubes, tourniquets, and bandages.

Personal Protective Equipment (PPE) Anyone performing venipuncture must protect against blood-borne pathogens by wearing gloves and a lab coat or apron. Face shields are usually not necessary, but they keep droplets out of the eyes if splatter is a concern. A puncture-proof biohazard container for used needles should be available. Today’s models are designed with lids that allow for safe, one-handed disposal.

Cleansing Pads Whenever the skin is broken, there’s potential for infection, so for routine venipuncture, alcohol is used to cleanse the area where the needle is inserted. It doesn’t sterilize skin, but when combined with a scrubbing motion, it decreases bacteria count and makes infection less likely.

Alternative agents with more disinfecting power, such as chlorhexidine or betadine, are recommend for high-risk individuals. Betadine, an iodine-containing product, was once considered a risk for anyone with a shellfish allergy, but studies show there is no cross-reaction.

Needles These come in various shapes and sizes. Medical assistants need to use their clinical judgment to make the best choice for their patients.

Needle diameter is measured in gauges from 16 to 32. The smaller the number, the bigger the needle is. For children, a 25 to 28 gauge size is ideal. Most adults require a 20 or 22 gauge, but patients who are petite, ill, or possibly dehydrated benefit from a smaller diameter needle. Large bore sizes exert more pulling pressure and could cause weak veins to collapse.

Needles also come in variable lengths to match the depth of the vein. Medical assistants should select the most appropriate length based on the size of the patient, the location of the vein, and the angle of approach. For convenience, most blood is drawn from the median cubital vein at the inside bend of the elbow, but in some patients, veins run too deep to reach with a standard one-inch needle.

Blood Collection Tubes Venipuncture was once performed with the same type of syringe used to give injections, but today, it’s done using vacuum tubes. A needle with a plastic cover on one end and a rubber sheath over the other is screwed into a universal needle holder. When the needle is inserted, a vacuum tube is pressed onto the back of the rubber-coated needle, perforating the stopper. The strength of the vacuum pulls blood out of the vessel.

Tubes come in different sizes, and every effort should be made to collect the necessary amount of blood in the fewest number of tubes. That requires knowing how much blood is needed for each test, as well as which require the same tube so they can be combined. Oversized tubes, however, like large needles, exert more pulling pressure on delicate veins and should be used judiciously.

Tourniquets These confine blood to the extremity from which it will be drawn. They keep the vein full and make it easier to locate, giving it a robust texture that holds up against the force of a needle.

Bandages When venipuncture is complete, the site is firmly compressed with gauze to stop bleeding, and a bandage is applied to keep any remaining drops off patient clothing.

Performing the Venipuncture

Choosing the right equipment and preparing supplies is more than half the battle with venipuncture. The actual process takes under a minute.

  1. Wash hands and apply gloves.
  2. Cleanse the skin.
  3. Place the tourniquet 3 to 4 inches above the vein to be punctured.
  4. Brace the vein, insert the needle, and push in the collection tube, removing the tourniquet once the needle is in place and adequate blood flow is established.
  5. Fill tubes completely until all of them have been collected.
  6. Remove the needle and apply pressure to the site with gauze.
  7. Cover the puncture with a small adhesive bandage.
Processing Samples

Once the venipuncture is complete, tubes are labeled with the patient’s name and the date and time of collection. Labels must be error-free, or samples may be rejected, resulting in delays in care or unnecessary redraws.

Samples are then processed. Some require separation in a centrifuge before they can be tested or sent to an outside lab. Others require immediate refrigeration or storage on dry ice for shipment. Each lab maintains a test catalog that details the sample processing each test requires.

The Benefits of Having Venipuncture Skills

Vocational school programs cover the basics of venipuncture, but it’s not everyone’s favorite task. It is, however, a valuable skill that shines on a résumé, and it opens the door to opportunity.

Medical assistants with venipuncture expertise can parlay that know-how into a full-time job in a practice where in-house blood tests are regularly done. With experience, they can also pursue additional certification as a phlebotomist that may allow them to work in hospitals.

Top-notch medical assistants are always in demand, but the more skills they can offer prospective employers, the brighter the future they have.

Final Thoughts

As more private practices become full service, the need for medical assistants comfortable with venipuncture will grow. Vocational school medical assisting programs teach students everything they need to know to perform venipuncture, but it’s a skill that requires willingness and experience to perfect.

Did learning about venipuncture interest you? Ready for an exciting new career in the medical assisting field?

The Medical Assistant program at Hunter Business School prepares competent, entry-level medical assistants in the cognitive (knowledge), psychomotor (skills), and affective (behavior) learning domains required for professional practice.

The Medical Assistant program provides hands-on experience in a real medical setting where you can foster professional relationships with actual patients. Medical Assistant students spend 160 hours in an externship in a professional medical environment where they are supervised and taught in order to gain valuable on-the-job training.

Contact us today to find out more about how to become a medical assistant on Long Island.