Several features of the blood are measured in the complete blood count.

The Red blood cell evaluates

Red Blood Cell Count: Red blood cells (RBCs), also called erythrocytes, are cells that carry oxygen from your lungs to the rest of your body. The RBC counts the number of red blood cells that are present in your blood sample. If your RBC count is too low, you may have anemia or another condition.
Hemoglobin: It is the oxygen-carrying protein in red blood cells that gives the cells their representative red color.
Hematocrit:  It measures the volume percentage of RBC (Red Blood Cells) in the blood. A hematocrit value of 30% means that there are 30 milliliters of RBC in 100 milliliters of whole blood. 
The CBC blood test also provides important information on various red blood indices including

Mean corpuscular volume (MCV) is a measurement of the average size of red blood cells.
Mean corpuscular hemoglobin (MCH) is a calculated measurement of the average amount of hemoglobin inside red blood cells.
Mean corpuscular hemoglobin concentration (MCHC) is a calculated measurement of the average concentration of hemoglobin inside red blood cells.
Red cell distribution width (RDW) is a measurement of the variation in the size of red blood cells.

White blood cell tests

White blood cells (WBC) count:  It defines the total number of white blood cells in your blood sample. WBC helps your body fight against infection. A CBC measures the number and five types of white blood cells present (neutrophils, lymphocytes, monocytes, eosinophils, and basophils). 

Platelet tests

Platelets(thrombocytes) assist in blood clotting. The platelet count is a test that measures the number of platelets in your blood sample.
Mean platelet volume (MPV) is a measurement of the average size of platelets.

The CBC blood test is a great indicator of overall health and detects a variety of diseases and conditions, such as infections, anemia, and leukemia. Any increase or decrease in cell counts can indicate an underlying medical problem. It can give you and your health provider a heads up that further investigation is required. A CBC is also done to keep track of an existing medical condition or treatment. 

A CMP blood test measures 14 different substances in your blood and provides significant information about your body's chemical balance and metabolism. The CMP is usually ordered as part of a routine checkup or when you are being monitored for a specific condition like hypertension or diabetes or are taking medications that may affect your kidney or liver.

A CMP includes tests for the following:

Glucose is the main energy source for the body's cells and a relatively steady amount of glucose is a must in the body. Glucose monitoring is usually done to detect diabetes.

Calcium is an important mineral and is required for the proper functioning of nerves, muscles, and heart.

Protein tests

Protein tests including Albumin, Total Protein, Albumin/Globulin Ratio are used to measure the number of proteins in the blood as they are imperative building blocks of all cells and tissues and are crucial for the overall growth and development of the body.

Electrolytes

Electrolytes are minerals that help the transportation of nutrients into the body's cells and assist in removing wastes out of the cells. Sodium, potassium, carbon dioxide, and chloride are electrolytes, which help regulate the body's fluid levels and its acid-base (pH) balance.

Kidney Tests

BUN/Creatinine Ratio, Creatinine with GFR, and Urea Nitrogen tests are required to assess kidney function.

Liver Tests

ALP (alkaline phosphatase), ALT (alanine transaminase), and AST (aspartate aminotransferase) are different enzymes made by the liver and part of the CMP panel.
Bilirubin is a waste product produced by the normal breakdown of red blood cells. This is used to evaluate a person's liver function or to screen for or monitor liver disorders.

This test measures both Total and Free Testosterone and can be ordered for both men and women. For men, this test evaluates testicular function where obesity, liver or thyroid disorders may change the testosterone binding proteins. For women, this test evaluates masculinization and hirsutism (unwanted male-pattern hair growth on a woman's face, chest, and back).

TSH is created by the pituitary gland, and that can be located at the base of the brain. The gland is used to regulate thyroid hormones. You can find the thyroid at the front of the neck and is butterfly shaped. The thyroid produces three main hormones - triiodothyronine (T3), thyroxine (T4) and calcitonin. Metabolism and growth are just some of the functions controlled by the thyroid. The thyroid gland and pituitary gland work together to make sure the right about of thyroid hormones are produced. When this system is disrupted it can play havoc on the body. A TSH can show how well the thyroid is working.

Triiodothyronine, Free T3, is not affected by certain protein levels causing them to remain more constant. This test will therefore assess abnormal binding protein disorders. Triiodothyronine (T3) is a thyroid hormone that plays a role in nearly every physiological process in the body. It plays a key role in development, growth, the regulating of heart rate, metabolism and the body's temperature. Possible thyroid issues can be hyperthyroidism, hypopituitarism, primary or secondary hypothyroidism and thyrotoxic periodic paralysis. A thyroid disorder can create symptoms of anxiety to constipation.

Most of the T4 in your body is bonded to protein, and a smaller portion (free) has not. This is why there is a free T4 test and a total T4 test. A free T4 test is usually preferred because from this test you can see how much is available for the body to use. This test can be ordered if a TSH has come back abnormal. Pregnancy can also affect your T4 levels.