Simply put, a needle’s gauge is the size of its opening. It’s a measurement of the inner cavity of the needle, the breadth of the hollow part of the needle. There are a variety of different needle gauges that have different uses in medical procedures. In the past few decades, needles have become increasingly narrow. This makes them less uncomfortable/painful to use and allows them to enter the body without causing unnecessary damage.
The higher the gauge size of a needle, the narrower the needle. Narrower needles might be useful for patients who have narrow or fragile veins, ensuring minimum damage is done and that collecting the sample is as pain-free as possible. Broader needles provide a more accurate basis for testing as collecting with these needles lessens the chance of hemolysis. Hemolysis is known to cause inaccuracies in test results and as such should be avoided wherever possible. The choice of needle gauge for each patient will be made after taking the patient’s comfort and the potential viability of the sample into account.