The consumption of food alters the levels of the following in the blood: glucose, albumin, phosphates, triglycerides, urea, hormones such as insulin and calcitonin, and enzymes such as transaminases or phosphatases.
The Spanish Association for Family and Community Medicine states that fasting for between eight and ten hours is generally recommended before a blood test is taken. This helps prevent any effects that food can have on determining certain chemical parameters from occurring.
The Red Cross in Madrid explains that glucose, or lipids (cholesterol or triglycerides), are some of the parameters that can be altered after eating, and it is the indicator that is most frequently tested.
Routine blood tests serve to detect how the organs are functioning. This group of tests are referred to as panels or profiles, depending on the organ that needs to be monitored, such as renal panels, liver panels, lipid panels, and thyroid panels, etc. Other tests serve to determine a diagnosis by establishing a pattern of abnormalities. Physicians are the ones that choose the tests to better understand a patient’s condition.
While urine tests analyze less than blood tests, when they are ordered it is also important that they be taken first thing in the morning. This allows for a more concentrated sample because it is an accumulation of all the waste products produced by the kidneys overnight.