Blood tests are ordered by doctors to check for certain diseases or infections. They are also ordered when doctors want to determine functioning of organs, and also to find out if treatments are working. To be more specific, a blood test helps doctors:
The lab technician draws a vial or tube of blood and analyzes it. Depending on the reason/condition for the test, the technician uses the whole blood to count the cells from the fluid. This fluid is also referred to as serum or plasma.
The fluid is tested to measure or detect various substances in the blood. Serum testing helps detect several health conditions in their early stages where lifestyle alteration alone can avert a health risk.
That said, blood tests alone can't detect or treat medical conditions. Blood tests are merely tools that confirm or deny a doctor's initial assessment of your health condition; they are done based on your symptoms and your medical history, and other tests, if any.
Of the lot, thyroid and liver functioning are the two conditions which rely on blood tests for initial diagnosis.
In fact, a blood test is the first step towards identifying liver damage. If there is damage, the blood will contain liver enzymes that have spilled over from the cells of the liver. Like most conditions, a normal blood test indicates no enzymes, while an abnormal blood liver functioning test indicates that liver enzymes were detected in the blood. Enzymes are proteins which speedup chemical reactions in the body. The most common and sensitive of the liver enzymes is aminotransferases. Spillage of this in the blood could be indicative of acute viral hepatitis A/B, pronounced liver damage as a result of toxins caused by overdose of acetaminophen, or even protracted collapse of the circulatory system that occurs when the liver does not receive fresh blood containing oxygen and nutrients.
Thyroid, as mentioned above, is the other condition that relies on blood tests for initial diagnosis. A thyroid blood test can identify several aspects of the condition including:
As the name implies, this test detects thyroid stimulating hormones in the blood. Abnormal blood tests indicate the presence of TSH.
This measures the unbound thyroxine levels in the bloodstream. High levels are indicative of hyperthyroidism and low levels imply hypothyroidism.
Like fT4, this measures the free unbound triidothyronine in the bloodstream. Here too, high levels suggest hyperthyroidism and low levels suggest hypothyroidism.
Thyroid blood tests also asses symptoms of depression, headaches, PMS, unexplained weight loss and/gain, fatigue, anxiety attacks, muscle and joint aches, hair loss, lack of concentration, infertility, and low libido.
A thyroid blood test can also identify thyroid imbalances occurring due to chronic disorders, nutritional deficiency, adrenal stress, or any enzyme deficiencies. Any of these aforementioned conditions could result in euthyroid sick syndrome, also referred to as functional hypothyroidism.
An abnormal thyroid blood test can also be indicative of elevated thyroid antibody levels which could be a prelude to diseases like Grave's disease, Hashimoto's thyroiditis, or postpartum thyroiditis.
A thyroid blood panel test can comprehensively detect thyroid hormones and antibodies, or lack thereof.