Getting a blood test

Blood keeps your body working to its maximum potential by delivering essential nutrients and oxygen to the cells. Then, it removes the waste, or carbon dioxide, and transports it to body organs and the digestive system. 

Blood work may be done at a medical facility, healthcare provider's office or blood lab. The lab technician, or phlebotomist, usually draws blood from a vein in your arm and follow the orders on your doctor's blood test prescription. Your doctor can order any of thousands of different blood tests.

The complete blood count (CBC) is one of the most common with most physicians requesting the results from a CBC for a routine health exam. This test also provides additional information about the blood makeup and organ functions of people who aren't feeling well. The CBC shows the number of white blood cells in your blood sample. These white blood cells defend your body against infections, allergies and parasites. People produce a greater number of white blood cells when they have an infection or allergic reaction. The CBC also evaluates the red blood cells, which transport oxygen from one part of the body to another. From this blood work, your healthcare provider also learns the number of platelets, or the cell fragments that are needed for blood clotting.

What blood tests measure

Blood tests also provide valuable information about minerals in your body. For example, doctors want to ensure their patients have enough calcium. Low levels of this mineral may suggest problems with the thyroid gland, kidneys or malnutrition. Too much calcium in the body may make a person feel very tired, weak and nauseated.

Blood tests can find out if the patient has high blood sugar levels, which are associated with diabetes. Before a test for glucose, or blood sugar, people often finish a drink with a lot of sugar. Then, the phlebotomist draws their blood a number of times over the several hours to measure the blood sugar content.

Other tests measure the electrolytes, such as potassium and sodium. Potassium, which is regulated by the kidneys, is needed for healthy nerves and muscles, including the heart. The kidneys also help control the amount of sodium in the body: Too much salt can raise blood pressure and cause heart problems and stroke.

With a blood test, doctors can identify a pregnancy earlier than a urine test done at home. They can also measure the amount of chorionic gonadotropin hormone (hGC) that's produced by a pregnant woman's placenta. This information can be very important for a physician who is concerned about pregnancy problems. Blood centers also perform tests to look for HIV, hepatitis B, herpes simplex virus, syphilis and other sexually transmitted diseases. Increasing numbers of companies are requiring new employees to have a blood test to screen for illegal drugs.

Preparing for a blood test

A health care provider will often order blood tests for conditions such as diabetes and high cholesterol, which requires you to fast for a certain amount of time before the test. The doctor or nurse will give you more information about how this fasting should take place.

For some labs, you'll need to make an appointment. Many walk-in facilities let you come in and wait for the next available technician, but be sure to give yourself plenty of time because your may have to wait a while if they're busy. If your doctor doesn't have the facilities to conduct blood work, he or she will likely refer you to a blood lab. Be sure to check Angie's List for other members' reports about labs in your area.

The lab technician will take different amounts of blood depending on the number of tests the doctor requires. The phlebotomist will place a tourniquet on your arm, so he or she can more easily see your veins before inserting a needle to draw blood. You'll feel a small pinch when the skin is pierced. When the phlebotomist finishes drawing your blood, he or she will apply some cotton and a bandage to stop the blood flow. You may notice some bruising the next day.


Hematology focuses on diagnosing and treating blood diseases and disorders, including hemophilia, anemia, malaria, blood clots, HIV and blood cancers such as leukemia and lymphoma. Hematologists are also trained to provide bone marrow transplants and blood transfusions.

LEARN MORE: Angie's List Guide to Hematology

Pediatric hematology

Pediatric hematologists specialize in diagnosing and treating blood diseases and cancers in children. Common blood disorders and diseases include anemia, leukemia, Non-Hodgkins lymphoma, hemophlia and lymphocytopenia.

LEARN MORE: Angie's List Guide to Pediatric Hematology

Blood banks

Blood banks and community blood centers collect donations of blood and blood products, such as platelets. In addition to collecting and screening blood donations, blood banks supply blood to area medical facilities.

LEARN MORE: Angie's List Guide to Blood Banks


Radiology uses diagnostic imagining to detect and diagnose illnesses and injuries. Imaging includes X-rays, fluoroscopy, CT cans, MRIs and PT scans.

LEARN MORE: Angie's List Guide to Radiology

Diagnostic laboratories

Diagnostic labs process diagnostic tests and provide the results to physicians. Types of labs include clinical pathology labs, which process blood, urine and tissue; gentics labs focusing on diagnosing genetic diseases; reproductive labs that conduct tests such as semen analysis; clinical chemistry labs that do blood analysis, such as drug and alcohol testing; and hematology labs that test and analyze blood cells.

LEARN MORE: Angie's List Guide to Diagnostic Laboratories

Ultrasound diagnostics

Ultrasound technicians use radiation-free imaging technology to diagnose potential health problems, discover unseen defects and examine the progress of healing from injuries or illnesses. Ultrasound technology is also frequently used during pregnancy to monitor the baby's health.

LEARN MORE: Angie's List Guide to Ultrasound Diagnostics

Leave a Comment - 6



Subject: U sure it's not menopause

U sure it's not menopause symtoms ?
I have got back to my normal weight since being off thyroid meds.


Subject: Thyroid

I'm taking medication for my thyroid, but I sweat when I'm asleep to the point of having to change my top. I also sweat some during the day. I can feel this coming on during the day, all most like a hot flash. It doesn't last too long. If I do any activity outside, the sweat will roll off of me. Before I started taking the medication, I would sweat profusely at night. It still isn't much better. I had my thyroid tested again after going on the med and it came back ok.
I'm just concerned as to why the sweating continues. I want to say it doesn't happen every day or every night.
Thank you,


Subject: I quit taking thyroid meds I feel better off them no matter what

My 8 year old had thyroid cancer. I was told had hasimotis. Quit taking med last year feel better no matter what blood tests showed.

rosalind pindyck

Subject: thyroid test

my tsh test is always ok,(slow) but they say ok,my aunt had hers removed 40 yrs ago and her son had thyroid cancer in his 60's now.
I am always cold , constipated,joint pain ,sever diabetic neuropathy and had BC stage 4 /32 yrs ago,is there another test I could take?? I eat very little and am 25 lbs over weight, cannot lose and take belly fat raspberry ketones and others and have really bad brain fog. I am 68 and 138 IQ play word with friend well but dont remember much leave the stove on:( cant find stuff everyday.


Subject: fibromyalgia and blood test

how can a blood test be true with someone with fibromyalgia they say that there is a certain kind of test or difference for us with this? Do you know of what it is? I think i have more wrong with my thyroids than we can find for my metabolism is really slow and i have constipation and sluggish all the time but they just think it is the fibro.

Greg Ashby

Subject: Blood test and fibro

I would do some research on the condition, "Hashimotto's

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