Approximately 10% of the population has needle phobia, or an intense fear of needles and sharp objects.
Fear of needles is a “specific phobia.” The Diagnostic and Statistical Manual (DSM-IV) lists a specific phobia as “marked and persistent fear that is excessive or unreasonable, cued by the presence or anticipation of a specific object or situation (e.g. flying, heights, animals, receiving an injection, seeing blood)”
There are several different phobias which fear of needles can fall under:
Belonephobia: fear of needles
Aichmophobia: fear of pointed objects
Trypanophobia: fear of injections
No matter what the name, however, needle phobia can cause problems when people avoid receiving medical care because of their fear. Today, the diagnostic process as well as preventive medicine regularly includes both injections and blood testing, both that require needles.
One common symptom of needle phobia is vasovagal reflex (fainting and possible loss of consciousness), tachycardia (rapid heart rate or heart palpitations) or hypertension (high blood pressure), even at the thought of having an injection or blood testing.
Needle phobia was once thought to be an emotional response to needles and a childhood fear, however, according to an article, “Needle Phobia: a Neglected Diagnosis”, by Dr. James G. Hamilton, this condition is “not confined to children, is not an emotion-driven or transient phenomenon, and is not a rare condition.” Dr. Hamilton explains that physicians must be aware and conscious of the condition because, “it is a common condition and because needle-phobic persons tend to avoid medical treatment, which can lead to serious health problems as well as social and legal problems.” 
Although most people have a genuine dislike of receiving an injection or having blood tested, the physical response in those with a needle phobia are more severe than in most people who simply find it unpleasant. Physical symptoms, such as the rise in blood pressure, increase in heart rate, increase in stress hormones or fainting (or dizziness) are measurable and, therefore, should be considered and addressed to help a patient when needles are a necessary part of medical treatment.
People with needle phobia often report an immense amount of pain associated with receiving an injection or having to have blood tested.