Getting a blood test typically starts with a doctor’s order, though you can also order certain tests yourself depending on where you live. The process is straightforward: you get a lab requisition, visit a collection site, have your blood drawn, and receive results within a few days. Here’s what each step looks like in practice.
Getting a Doctor’s Order
The most common route is through your primary care provider. During a routine checkup or sick visit, your doctor decides which tests you need based on your symptoms, age, or health history, then sends an order to a lab. That order can be transmitted as a signed document, a phone call, a fax, or an electronic message to the testing facility. You’ll usually receive a paper or digital requisition form to bring with you to the lab.
If you don’t have a primary care doctor, urgent care clinics and telehealth services can also write lab orders. Many telehealth platforms let you request common panels online, and a licensed provider reviews and approves the order without an in-person visit.
Ordering Tests Without a Doctor
Direct-to-consumer testing lets you order blood work on your own, without a prior doctor visit. Companies like Quest Diagnostics, Labcorp, and several online platforms sell individual tests or panels that you purchase, then visit a local lab to have your blood drawn. A physician affiliated with the service signs off on the order behind the scenes to satisfy lab regulations.
Not every state allows this. State laws govern who can order and receive lab results, so direct-access testing is restricted or unavailable in some areas. If you live in a state that permits it, you can typically browse a test menu online, pay out of pocket, and schedule a draw at a nearby collection site. Insurance rarely covers these self-ordered tests, so expect to pay the listed price upfront.
Common Tests and What They Measure
Two of the most frequently ordered panels are the complete blood count (CBC) and the comprehensive metabolic panel (CMP). A CBC looks at your red blood cells, white blood cells, and platelets, giving your doctor a snapshot of your immune function, oxygen-carrying capacity, and clotting ability. It’s often the first test ordered when something seems off.
A CMP measures 14 substances in your blood and covers a lot of ground. It checks your blood sugar, calcium levels, and four electrolytes (sodium, potassium, bicarbonate, and chloride) that help regulate fluid balance. It also measures proteins made by your liver, three liver enzymes, bilirubin (a waste product from broken-down red blood cells), and two markers of kidney function. Together, these numbers tell your provider how well your liver and kidneys are working, whether your blood sugar is in range, and whether your body’s chemical balance is healthy.
Other common orders include a lipid panel for cholesterol, thyroid function tests, a hemoglobin A1C for long-term blood sugar control, and vitamin D levels. Your provider picks the specific tests based on what they’re screening for or monitoring.
How to Prepare Before Your Draw
Some tests require fasting, which means no food or drinks other than water for 8 to 12 hours beforehand. The tests that most commonly require fasting are blood glucose tests, cholesterol panels (lipid panels), and basic metabolic panels. Liver and kidney function tests may also require fasting when they’re ordered as part of a larger panel like a CMP. If you’re unsure, ask when you schedule the appointment. Morning appointments make fasting easier since most of the window falls overnight.
Supplements can also affect your results. Biotin, a B vitamin found in many hair, skin, and nail supplements, can significantly interfere with certain lab tests and produce incorrect results. The FDA has flagged biotin as a concern because the interference often goes undetected. If you take a biotin supplement, mention it to your provider or the lab staff before your draw. You may be asked to stop taking it for a few days beforehand.
Drink plenty of water in the hours before your appointment. Staying hydrated makes your veins fuller and easier to find, which means a quicker, smoother draw.
What Happens During the Draw
The person drawing your blood (a phlebotomist) will start by washing their hands and putting on gloves. They’ll tie a tourniquet around your upper arm to make your veins more visible, then feel for a good vein with their fingertip, usually at the inside of your elbow. You may be asked to make a fist, which helps the vein stand out. The tourniquet stays on for less than a minute to avoid affecting your results.
After cleaning the site with an antiseptic wipe, the phlebotomist inserts a small needle at a shallow angle. You’ll feel a brief pinch or sting. Blood flows into one or more collection tubes, the tourniquet comes off, and the needle is removed. The whole process takes about one to three minutes for a standard draw. A small bandage goes over the site, and you’re done.
If your inner-elbow veins aren’t accessible, the phlebotomist may use a vein on the back of your hand or, less commonly, the wrist. Wrist draws carry a slightly higher risk of nerve irritation, so they’re typically a last resort.
Managing Needle Anxiety
Fear of needles is common and nothing to be embarrassed about. One effective technique is applied muscle tension: repeatedly tense the large muscles in your legs, arms, and core for 10 to 15 seconds at a time, then release. This raises your blood pressure slightly and helps prevent the lightheaded, fainting feeling that some people experience during a draw.
Distraction works well too. Watching a video on your phone, listening to music, or talking to the phlebotomist can shift your focus away from the needle. Looking away from the draw site is a simple move that helps many people. Deep, slow breathing before and during the stick can also lower your anxiety response. If your fear is severe enough that you avoid medical care, exposure therapy with a therapist has strong evidence behind it and can resolve the phobia in just a few sessions.
Getting Your Results
Most standard blood tests return results within 24 to 48 hours. More complex tests may take up to two weeks, and specialized panels like genetic testing can take up to 21 days. Many labs now post results to an online patient portal as soon as they’re finalized, sometimes before your doctor has reviewed them.
Your lab report will list each test alongside a reference range, which represents the high and low ends of what’s considered normal based on results from large groups of healthy people. If a result falls outside that range, you’ll typically see it flagged with an “H” for high or “L” for low. One important detail: different labs use different testing methods and different reference ranges, so always compare your results to the specific range printed on your own report rather than numbers you find online.
A single out-of-range result doesn’t necessarily mean something is wrong. Dehydration, recent meals, supplements, stress, and even the time of day can shift certain values. Your provider interprets the full picture, including your symptoms, history, and how far outside the range a number falls, before deciding whether a result is clinically meaningful or needs a repeat test.