lab technician holding blood vials

Fasting for Bloodwork Explained for Different Types of Blood Tests

When you go to the doctor, they may want to run some blood tests to get more information about your health and how it might affect your life. There are many blood tests, ranging from basic blood work to check your overall health to genetic testing to detect predispositions to certain diseases or conditions. Here’s what you need to know about some of the main types of a blood tests, why people might need them, and whether you’ll need to fast beforehand (and if so, how long).

What is a blood test?

A blood test is a diagnostic procedure involving taking a blood sample from a person to test for certain markers or diseases. Blood tests can assess various things, including someone’s overall health, whether they have an infection, and whether they have any underlying medical conditions.

It’s important to note that some blood tests don’t require a person to fast before being administered. If you need a routine blood test and your doctor hasn’t specified otherwise, you likely won’t need to abstain from food or drink before taking it.

Reasons to get a blood test

A blood test is a way to check your health by testing a blood sample. Blood tests can show if you have an infection, if you have a disease, or if you are at risk for other medical problems. You may need a blood test for disease symptoms, such as fatigue or weight loss. Blood tests can also check how well your organs are working. For example, a blood test can show how well your liver works. Some of the most common blood tests include

  • Complete blood count
  • Basic metabolic panel
  • Comprehensive metabolic panel
  • Lipid panel
  • Thyroid panel
  • Cardiac biomarkers
  • Sexually transmitted infections
  • Coagulation panel
  • DHEA sulfate serum
  • C reactive protein

Depending on your situation, the tests may be routine like complete blood count, basic metabolic panel, or thyroid panel, or may be used for specific situations like enzyme markers or sexually transmitted infection. All the results should be taken seriously as they are important to your overall health. Some tests like complete blood count can show signs of cancer in the body.

Blood work testing process

A few steps go into getting your blood drawn for testing. First, you must make an appointment with your doctor or a local lab. Then, you may need to fast for a specific amount of time before your appointment. The reason for this is so that your results will be accurate. After you have fasted, you will go in and have your blood drawn. The steps taken for bloodwork being drawn include

  • Cleaning the area where blood will be drawn
  • Rubber band your arm to make veins more visible
  • Insert need with a tube attached to draw blood
  • Remove the needle and takes off the rubber band
  • Clean up the drawing site and bandage it

Blood testing is typically done in a hospital or clinic setting. Still, over the years, it has become an increasingly popular test with at-home testing services such as concierge or mobile medical services. These services offer the same testing process but include the convenience and comfort of doing it at your home or office. No need to waste time traveling to a clinic across town. Simply schedule a time that works for you. They’ll show up at your location and take care of the rest!


Overall, blood work risks are very minimal. It’s a straightforward process but can include slight discomfort when the needle goes in fainting or vein puncture.

When you fast for blood work, you deprive your body of calories and nutrients. This can cause low blood sugar levels, leading to lightheadedness or dizziness. You may also experience headaches, irritability, and difficulty concentrating. If you have any medical conditions, speak with your doctor before fasting for blood work.

Fasting before blood tests

Fasting before blood work is important because the body needs to empty the stomach of any liquids and food particles so that they don’t mix with the blood and affect the lab readings. Depending on the type of blood test, some may require an overnight fast, while others can be done after just a few hours.

Most people have fasted before a blood test at some point in their lives. Whether for a routine physical or something more serious, fasting is often required to get accurate results. But why is this? And how long do you need to fast for different blood tests? Let’s take a look at some types of tests that require fasting.

Cholesterol tests

Cholesterol is a type of fat found in your blood. Too much cholesterol can lead to plaque buildup in your arteries, leading to heart disease. A cholesterol test can help determine if you have high cholesterol and are at risk for heart disease. For this reason, people tested for cholesterol should avoid eating or drinking anything 9 to 12 hours before the test.

Blood sugar tests

More than 11% of Americans are diabetic. If you have diabetes, your doctor will likely order a fasting blood sugar test to diagnose the condition. For this test, you must overnight fast before your blood can be drawn. The test measures the sugar in your blood and can help your doctor determine if you have diabetes or pre-diabetes. Overnight fasting means not eating anything except water from 8 pm the night before until after the morning exam.

Liver function tests

Liver function testing is used to detect the presence of liver disease and may be ordered by a healthcare provider if they suspect the liver may not function correctly. Fasting is typically required before these tests for 10-12 hours, depending on the test being performed. Results will show abnormal levels of certain bodily substances and liver enzymes (including ALT, AST, and GGT). The tests are often used to determine if there are any underlying causes for symptoms such as weight loss or nausea.

Kidney function tests

If your doctor suspects you have a kidney problem, they may order a kidney function test. This test measures how well your kidneys can filter waste from your blood. You will need to fast for at least 8 hours to get accurate results before the test. Results will show levels of creatinine, urea nitrogen, and electrolytes. These values indicate whether or not there is an issue with the kidneys that needs treatment.

Basic metabolic panel

The Basic Metabolic Panel (BMP) is a group of blood tests that give your doctor important information about your metabolism. This test can help diagnose diabetes, kidney disease, and other disorders.

You may need to fast for this test. Fasting means not eating or drinking for at least 8 hours before the test. These results are based on whether certain proteins are present in the bloodstream at abnormal levels. Some BMP tests measure ketones (compounds made when fats break down), electrolytes (chemical substances in cells and body fluids), cholesterol levels, liver enzymes, sugar levels in the blood or urine, red blood cell count, white blood cell count, and more.

Glucose test

A glucose test is a type of blood test used to determine the amount of sugar in your blood. Sugar, or glucose, is a major energy source for your body. Too much or too little sugar in your blood can be harmful. A fasting glucose test is done first thing in the morning before eating or drinking anything. The type of fasting recommended for glucose testing is an overnight fast (eight hours). Other types of fasting may also be appropriate, depending on the situation. If there are concerns about pre-diabetes, diabetes, or uncontrolled diabetes (high blood sugar), this should be discussed with your doctor.


No matter what type of blood test you have done, the process is generally the same. A health care professional will take a sample of your blood by inserting a needle into a vein in your arm. The results usually take 24-72 hours to return from the lab.

Depending on the test, results may indicate further treatment is needed to bring any abnormal levels back to a healthy range. Treatments may include lifestyle changes or a form of medicine. There are many treatments available that are unique to each situation. Discussing your results with your healthcare provider to get you back on track to a healthy lifestyle is best.


Blood tests are extremely common. Preparation can vary from test to test, but the most basic is that a person needs to fast for at least 8 hours before the test (or as instructed by the doctor). Sometimes, it may be necessary to stop eating and drinking before 8 pm the night before.

It’s important to get common blood tests done regularly to help detect early signs of illness or disease. People with illness symptoms should see their doctor and request a blood test. If they have no symptoms, they should still request one if they haven’t had one in over six months or yearly if there’s a family history of certain diseases like diabetes or heart disease.

Get your at Home Lab Test with Concierge MD

If you need a lab test but want to avoid traveling to the doctor’s office, consider Concierge MD as an option. We are a licensed mobile healthcare provider with a wide range of services, including lab testing. You can make an appointment online or over the phone for one of our healthcare specialists to visit you in your home and collect samples for one of our many accessible lab tests:

  • Wellness Panel
  • Male Hormone
  • Female Hormone
  • STD Panel
  • Thyroid Panel
  • Anemia Panel
  • Food Sensitivity
  • Genetic Cancer Screening
  • Micronutrient
  • Gut Microbiome
  • Inflammation Panel
  • Heavy Metal Panel
  • Sleep and Stress Panel
  • Urinary Health Panel
  • Vaginal Health Panel
  • and more… 

Our staff will assure the safe delivery of samples to our lab. When your results are ready, we can assist you in interpreting them and help you move forward toward a better self. Concierge MD is a private and professional healthcare service that focuses on you. Contact us immediately to order your lab testing!

Experience Care with ConciergeMD

ConciergeMD offers coverage throughout the United States.