Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
Normally, cortisol levels rise and fall during the day, repeating on a 24-hour cycle (diurnal variation). Highest levels are at about 6 - 8 a.m. and lowest levels are at about midnight.
Physical and emotional stress can increase cortisol levels, because during the normal stress response, the pituitary gland increases its release of ACTH.
Higher than normal cortisol levels are expected in women who take estrogen or birth control pills.
Stewart PM. The adrenal cortex. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008: chap 14.
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