What is a helpful technique for patients with hard-to-find veins?

Recommending that the patient properly hydrate before their blood draw is the most clinically appropriate technique for improving venous access in patients with hard-to-find veins. Adequate hydration increases plasma volume and causes veins to fill and become more distended, making them easier to palpate and visualize. Dehydration causes blood to become more viscous and veins to collapse and become difficult to locate. Using a blood pressure cuff and inflating it to 15 to 20 mmHg is too low to function as a tourniquet; standard tourniquet pressure is typically 40 to 80 mmHg, just above diastolic pressure, to distend superficial veins while allowing arterial inflow. Pumping to only 15–20 mmHg would not occlude venous return adequately. Recommending a large meal the night before is not an evidence-based strategy and may actually interfere with fasting laboratory values if those are required. Having the patient perform 15 to 20 jumping jacks immediately before the draw is impractical in most settings, could elevate certain lab values spuriously through exercise-induced changes, and is not a standard recommendation. Warm compresses and gravity-dependent positioning are other accepted strategies for patients with difficult venous access.