Final answer:
For drawing blood from an obese patient, the median cubital vein in the antecubital region is commonly used due to its superficial location and ease of accessibility. In some instances, the cephalic vein may also be considered if it is clearly visible and palpable.
Step-by-step explanation:
The vein commonly used to draw blood from an obese patient is the median cubital vein. This vein is part of the superficial venous network of the upper limb and is often easier to access due to its size and superficial location in the antecubital region, the area of the arm opposite the elbow. For obese patients, this vein can be more palpable and accessible than others because it lies within a fat pad that is easier to penetrate than surrounding areas with denser adipose tissue.
It is important to note, however, that the cephalic vein may also be considered in some cases, starting in the forearm and draining blood from the superficial surface of the arm into the axillary vein. It is highly superficial and can sometimes be seen along the surface of the biceps brachii muscle, which may make it a viable option for venipuncture in individuals with good muscle tone and those with less subcutaneous adipose tissue in the arms.