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The Surprising Truth: What Really Happens When You Eat Before Blood Work

  • Post published:June 23, 2023
  • Post category:Blog

blood work

When it comes to blood work, you may have heard that fasting is often required. It’s common advice to abstain from eating or drinking anything except water for a specific period before your blood test. But have you ever wondered why fasting is necessary? What really happens if you eat before blood work? In this article, we will uncover the surprising truth and shed light on the impact of eating before blood tests.

Understanding Blood Work

Blood work involves the analysis of blood samples to evaluate different aspects of a person’s health. It can provide valuable information about cholesterol levels, blood sugar, liver and kidney function, nutrient deficiencies, and much more. Depending on the purpose of the test, healthcare providers may request certain preparations, such as fasting, to ensure accurate results.

Importance of Fasting for Blood Work

Fasting before blood work is important because it helps ensure accurate and reliable test results. When you eat, your body metabolizes the food, breaking it down into various nutrients that circulate in your bloodstream. These nutrients can affect the composition of your blood, potentially altering the results of certain tests. Fasting allows healthcare professionals to obtain a baseline measurement of your body’s normal state, unaffected by recent meals.

Where To Get Tested?

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Exceptions to Fasting

While fasting is commonly required for certain blood tests, it’s important to note that not all tests necessitate it. Some tests, such as routine cholesterol screenings or complete blood counts, do not typically require fasting. It’s crucial to follow your healthcare provider’s instructions regarding fasting or eating restrictions specific to your blood test.

Guidelines for Eating Before Blood Work

If fasting is required for your blood test, it’s essential to follow the guidelines provided by your healthcare provider. Typically, fasting involves refraining from consuming any food or beverages, except for water, for a specific duration. The fasting period can vary depending on the test, ranging from 8 to 12 hours. It’s crucial to adhere to these guidelines to ensure accurate results.

Preparing for Your Blood Test

To prepare for blood work, it’s important to communicate with your healthcare provider and understand the requirements for your specific test. They will provide you with detailed instructions, including whether fasting is necessary and the duration of the fasting period. Make sure to clarify any doubts or concerns you may have to ensure a smooth testing experience.

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What Happens When You Eat Before Blood Work?

If you eat before blood work, your body will digest the food and release glucose into your bloodstream. This increase in blood sugar levels can impact tests that measure glucose, such as fasting blood sugar or glucose tolerance tests. Additionally, eating fatty foods can lead to increased triglyceride levels, affecting tests that evaluate cholesterol and lipid profiles.

Impact on Blood Test Results

Eating before blood work can lead to inaccurate test results, which may misguide healthcare professionals in diagnosing and monitoring certain conditions. For example, if you consume a high-carbohydrate meal before a fasting blood sugar test, your blood glucose levels will be higher than expected, potentially leading to a misdiagnosis of diabetes or impaired glucose tolerance.

Common Tests Affected by Eating Before Blood Work

Certain blood tests are particularly sensitive to the influence of food. Here are some common tests that can be affected by eating before blood work:

Fasting Blood Sugar

Eating prior to a fasting blood sugar test can result in elevated glucose levels, leading to inaccurate readings.

Lipid Profile

Consuming fatty foods before a lipid profile test can increase triglyceride levels, affecting the evaluation of cholesterol and lipid levels.

Glucose Tolerance Test

Eating before a glucose tolerance test can interfere with accurate measurements of how your body handles sugar, potentially masking conditions like prediabetes or diabetes.

Common Blood Tests Requiring Fasting

Several blood tests commonly require fasting to obtain accurate results. These include:

Lipid Profile: Measures cholesterol and triglyceride levels.

Fasting Blood Glucose: Evaluates blood sugar levels.

Basic Metabolic Panel: Assesses kidney and liver function, electrolyte levels, and blood sugar.

Renal Function Panel: Analyzes kidney function and electrolyte levels.

Iron Panel: Measures iron levels in the blood.

Remember, this is not an exhaustive list, and your healthcare provider will inform you if fasting is necessary for your specific blood test.

Potential Effects of Eating Before Blood Work

Eating before blood work when fasting is required can potentially impact the accuracy of the results. Consuming food or certain beverages can lead to increased levels of glucose, triglycerides, or other substances in the blood, influencing the interpretation of the test. To ensure reliable results, it’s crucial to adhere to the fasting guidelines provided by your healthcare provider.

Factors to Consider

Several factors may affect the fasting requirements for blood work. These include:

  • The type of test being conducted
  • The specific markers being measured and
  • Your overall health condition

If you have any chronic conditions, take medications, or have dietary restrictions, it’s important to discuss these factors with your healthcare provider to determine the appropriate fasting guidelines for your blood test.

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Tips for Proper Fasting Before Blood Work

To ensure accurate results and minimize the risk of misleading diagnoses, it is crucial to follow proper fasting guidelines before blood work. Here are some tips to help you fast effectively:

Check fasting requirements: Consult your healthcare provider or the lab conducting the blood test to understand the specific fasting instructions for your test.

Water is allowed: Unless instructed otherwise, you can usually drink water during the fasting period. Staying hydrated is essential.

Plan your timing: Schedule your blood test for the morning to minimize the duration of the fasting period.

Take medications as prescribed: If you are on medications, check with your healthcare provider if you should continue taking them during the fasting period.

Be mindful of hidden sources of calories: Some medications, supplements, or even chewing gum may contain calories that can break your fast. Read labels carefully and avoid such products.

Alternatives to Fasting

While fasting is generally recommended for accurate blood test results, there may be alternatives available for certain tests. Some healthcare providers may offer non-fasting options, such as random blood sugar tests or postprandial blood sugar tests, which assess glucose levels after a meal. It’s important to consult your healthcare provider to determine if these alternatives are suitable for you.

Is fasting required for all blood tests?

No, fasting is not required for all blood tests. However, certain tests like fasting blood sugar, lipid profiles, and glucose tolerance tests often require fasting to obtain accurate results.

How long should I fast before blood work?

The fasting period can vary depending on the specific test. Typically, it ranges from 8 to 12 hours. Consult your healthcare provider or the lab for the recommended duration.

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Can I drink water during the fasting period?

In most cases, you can drink water during the fasting period. However, it’s important to follow the specific instructions provided for your blood test.

What happens if I accidentally eat before blood work?

If you accidentally eat before blood work, it’s essential to inform the healthcare provider or the lab conducting the test. They may advise rescheduling the test or opting for alternative non-fasting options.

Are there any risks associated with fasting for blood work?

Fasting for blood work is generally safe for most individuals. However, if you have specific medical conditions or take medications that require food intake, it’s important to consult your healthcare provider to ensure fasting is appropriate for you.


Fasting before blood work plays a crucial role in obtaining accurate test results. Eating before blood tests can impact various measurements, potentially leading to misleading diagnoses. By following proper fasting guidelines and understanding the importance of this practice, you can ensure that your blood work provides healthcare professionals with valuable and reliable information about your health.

Mobile Phlebotomist

Mobile Phlebotomist

Our licensed mobile phlebotomists provide at-home blood draws used to evaluate your health and well-being. Blood tests reveal how well organs function, predict the risk of certain diseases, help diagnose certain medical conditions, and monitor any adverse effects of medications you take.

Speedy Sticks makes it easy to schedule an appointment because we come to you. To find out how we can build a healthcare experience around your needs contact us today.

Complete Blood Count

A complete blood count (CBC) is a blood test that provides information about your red blood cells, white blood cells, and platelets. The results of this test can supply information about your overall health and detect medical conditions such as:

  • Infections
  • Anemia
  • Inflammation
  • Leukemia
  • And some cancers

Basic Metabolic Panel

You can learn how your body uses or metabolizes food for energy with a basic metabolic panel. This blood test indicates how well your kidneys function and the level of your blood sugar or glucose. It also measures other essential blood elements such as potassium, sodium, and calcium. This test is used to diagnose kidney problems or monitor the effects of medicines you take on your kidneys.

Comprehensive Metabolic Panel

comprehensive metabolic panel is used for a wider assessment of your health and well-being. It includes the same tests as the basic metabolic panel plus several more. This panel of tests helps reveal how well your kidneys and liver function, your levels of blood sugar, protein, and electrolytes, and the health of your metabolism.

Lipid Panel

Lipids are important fats that provide energy and help your body function well. However, lipid disorders can cause coronary artery disease, stroke, and heart attack. A lipid panel measures blood cholesterol and other lipids that are leading causes of these diseases. The findings of your lipid panel include measurements of total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides. 

Thyroid Panel

Every cell in your body depends on a properly functioning thyroid gland for adequate levels of critical hormones. These thyroid hormones regulate how you burn calories to affect weight gain or loss. Your thyroid also plays a role in your heart rate, body temperature, digestion, and muscle function. A thyroid panel measures the level of these vital thyroid hormones.

Enzyme Markers

Billions of chemical reactions take place every second in the human body. Proteins known as enzymes help speed up these reactions for healthy digestion, breathing, muscle formation, and nerve function. Blood tests called enzyme markers will evaluate the presence of specific enzymes to help diagnose and monitor certain conditions of the heart, liver, and digestive tract.

Coagulation Panel

A coagulation panel analyzes the components necessary for normal blood clotting. Without adequate results of factors such as: Vitamin K, Proteins such as fibrinogen, Calcium,
Platelet levels, Bone marrow, and others, wound healing would not occur due to excessive bleeding. This test helps ensure your blood is capable of healthy clotting.

The C-reactive Protein Test

A C-reactive protein blood test determines how much C-reactive protein is circulating in a patient’s blood to test for specific conditions, such as infections and autoimmune disorders. This protein is not normally present in large amounts and can signal an infection or chronic issue if your levels test above average.

DHEA Sulfate Serum Test

DHEA stands for dehydroepiandrosterone. It is a hormone in both male and female bodies, produced by our adrenal glands. DHEA is responsible for many developmental traits, such as making both the male and female sex hormones (testosterone and estrogen, respectively). When DHEA is low it can be a sign of problems, this DHEA Sulfate Serum test measures your DHEA levels.

MCV Blood Test

The mean corpuscular volume MCV blood test is a standard diagnostic tool that measures the size of red blood cells in a patient’s bloodstream. Simply put, it determines the average volume of red blood cells in a blood sample.

MCH Blood Test

MCH stands for a mean corpuscular hemoglobin test. Better known as the MCH blood test. It is a diagnostic tool that measures the average amount of hemoglobin in each red blood cell in a patient’s bloodstream. Hemoglobin is the protein that carries oxygen in the blood, and its levels can provide important diagnostic information about a person’s health.

MPV Blood Test

An MPV blood test measures the average size of your platelets, the blood cells that help your blood clot. When considered alongside other test results on a complete blood count (CBC), an MPV test can help your healthcare provider diagnose blood disorders and other conditions.

AST Blood Test

The aspartate aminotransferase (AST) test is a blood test that checks for liver damage. Your doctor might order this test to find out if you have liver disease and to monitor your treatment.

SpeedySticks makes it easy to schedule an appointment because we come to you.

To find out how we can build a healthcare experience around your needs contact us today.

Complete Blood Count Test

Blood performs the essential tasks of transporting oxygen, nutrients, and hormones to all parts of your body. At the same time, it removes harmful waste products from your kidneys, liver, and lungs. These vital functions depend on a healthy number of unique cells found in the blood. A complete blood count test provides valuable information about these cells and your overall health.

SpeedySticks makes it easy to schedule an appointment because we come to you. To find out how we can build a healthcare experience around your needs contact us today.

What Is A Complete Blood Count?

The blood that flows through your arteries and veins contains three life-sustaining cells, red blood cells, hemoglobin, and white blood cells. The number of each cell type must be kept within a normal range to keep you healthy. When the cell numbers are too many or too few, it indicates a condition, disease, or disorder that requires medical attention.

A CBC test measures the numbers of these cells and provides a good indication of how well your body functions each day.

How Do You Prepare For A Complete Blood Count?

Unless you have other blood tests performed the same day, you will not need to fast for the complete blood count test. Your mobile phlebotomist will prepare your arm and withdraw the blood. You may feel a slight pinch but no pain during the test. After the test, your provider places a small bandage over the withdrawal site, and your body quickly restores the small amount of withdrawn blood volume.

Why Is A Complete Blood Count Used?

A CBC can be a part of a regular assessment of your health and to evaluate any possible adverse effects of some prescription medications. The results of a CBC offer information about:

  • Your overall health.
  • The presence of some medical conditions or diseases.
  • The sudden effect of a chronic illness, such as kidney disease, on your blood count.
  • Symptoms you experience such as weight loss, fatigue, bruising, or fever.
  • The diagnosis of blood disorders such as leukemia, sickle cell, and lymphoma.

What Does A Complete Blood Count Measure?

A complete blood count supplies important information about the number and function of these blood components:

  • Red blood cells. These cells carry oxygen from the lungs to other vital organs and the rest of the body. They also transport carbon dioxide from the body to the lungs for exhalation.
  • White blood cells. White blood cells help fight bacteria and viruses to prevent infections and diseases.
  • Platelets. Platelets are essential cells in blood clotting.
  • Hemoglobin. This blood protein contains iron and is vital in transporting oxygen.

What Are Normal Results For A Complete Blood Count?

The normal ranges for a CBC can vary according to several variables, including your age, gender, and the altitude where you live. In general, some of the CBC normal results are:

  • Red Blood Cell count in million cells/mcL: 4.5 to 6.1 for men and 4.1 to 5.1 for women.
  • White Blood Cell count in cells/mcL: 4.500-11,000.
  • Hematocrit: 41.5% to 50.4% for men and 35.9% to 44.6% for women.
  • Hemoglobin in grams/dL: 14.0 to 17.5 for men and 12.3 to 15.3 for women.
  • Platelets: 150,000 to 450,000 platelets/mcL.

When Should I Get A Complete Blood Count Test?

This important blood test can be part of your regular health checkup or if you notice specific symptoms, such as:

If you’re experiencing any of the symptoms above visit your Dr and find out if you need to have a complete blood count test completed. When or if your Dr orders a complete blood count test and you want to skip the lines, SpeedySticks can come to you in your own home when you contact us.

What Else Do I Need To Know?

*This content is for informational purposes only and is not meant to replace consulting with a healthcare professional. Please consult with your primary care physician or healthcare provider before engaging in any services offered by Speedy Sticks.