What to do if i have to get a blood test but severe needle phobia?

Let the lab know : before hand. Breath in slowly & deeply through your nostrils. Fill your lungs with air (but not to the point of discomfort). Hold for a count of five then slowly begin to exhale through an open mouth. Repeat at least 12 times, longer if you need to. If you haven't been assessed for your phobia- that would be prudent. Anxiety is no fun BUT it is treatable.