Final answer:
The angle of entry for a butterfly needle into a hand vein should be between 10 to 30 degrees to ensure accurate insertion without damaging the vein.
Step-by-step explanation:
The angle of entry for a butterfly needle into a hand vein should be shallow, typically between 10 to 30 degrees relative to the skin surface. Using too steep of an angle can cause the needle to puncture through the vein, while too shallow of an angle might not allow the needle to access the vein properly. The exact angle can vary depending on the gauge of the needle, the anatomy of the patient's veins, the practitioner's experience, and whether the vein is at the surface or deeper within the tissue. Venipuncture requires precision and care to ensure the butterfly needle is inserted correctly without causing excess discomfort or damage to the vein.