As the Merck Manuals explain, the body is able to control blood pressure by expanding and constricting blood vessels. This allows the body to raise blood pressure when it is low and also allows the body to regulate the amount of blood that gets to tissues at any given time.

Blood vessels deliver blood from the heart to the tissues, and return oxygen-depleted blood to the heart. The vascular system is made up of three vessel types.

Red blood cells carry oxygen from the lungs to the rest of the body. A high number of red blood cells--more than 5.72 million red blood cells per mcL for men and 5.03 million per mcL for women--requires further evaluation, according to MayoClinic.com.

The majority of iron in the blood is bound to hemoglobin, the oxygen-transporting protein. Blood iron that is not in hemoglobin may be in transit and bound to the protein transferrin. Iron that comes from body stores is in the form of a protein called ferritin.

Dangerously high blood glucose levels--over 300 milligrams per deciliter (mg/dL)--can cause life-threatening complications. Diabetic ketoacidosis (DKA) occurs mostly in type 1 diabetics, but can occur in type 2 diabetics in some cases. In DKA, insulin stores are exhausted and fats are broken down to use as energy.

Stress can be a positive or negative event. Getting married or buying a new home can be just as stressful as financial or health problems. Stress becomes a problem when it occurs on a regular basis with no break and creates feelings of being out of control or overwhelmed.

All blood is not created equal. It all serves the body, it delivers oxygen and nutrients. It polices, attacking what it perceives to be invaders. But what it perceives to be invaders changes from person to person.

Hypoglycemia, or low blood sugar, most commonly occurs among diabetics, people taking certain medications or those with deficiencies of specific hormones and enzymes. But among people who are desperately trying to lose weight, not eating enough food or exercising too much can cause extremely low blood sugar levels.

The medical term for low serum carbon dioxide levels is hypocapnia. It is usually caused by hyperventilation -- known as acute hypocapnia -- but can also result from asthma or hindrances to cerebral autoregulation, which is the disrupted regulation of blood flow in the brain due to tumors, hematomas or injuries.

Platelets are microscopic cell fragments found in your blood that help to form blood clots. If your platelets are too low, you may be at risk of bleeding and require a platelet transfusion.

Many health benefits are associated with drinking a moderate amount of alcohol each day -- such as lowering blood pressure, improving insulin sensitivity and reducing risk of developing cancer and heart disease. However, excessive alcohol intake can have negative health effects, such as liver disease and cancer.

Your blood sugar levels affect your mood and energy levels. Blood sugar is readily available energy that the body can use to fuel various processes. The body normally regulates its blood sugar through a chemical called insulin, which breaks down blood sugar.