Smart Labs Now Logo

¡Hablamos Español!

Folate & Vitamin B12 Blood Testing: Comprehensive Explainer

Folate and Vit B12 Blood Test Guide

Maintaining optimal levels of folate and Vitamin B12 is crucial for various bodily functions, including the production of red blood cells, DNA synthesis, and proper neurological function. Blood tests for folate and Vitamin B12 help diagnose deficiencies and monitor related health conditions.

This guide provides a comprehensive overview to empower prospective test-takers with all the information they need.

PART I: The Folate Blood Test

Folic Acid

Purpose of the Test

The folate blood test evaluates the levels of folic acid (vitamin B9) in the blood, an essential nutrient for the formation of red blood cells and DNA synthesis. Testing is often recommended to diagnose deficiencies or monitor conditions such as anemia, malnutrition, and malabsorption.

Folate deficiencies can lead to megaloblastic anemia, a condition where red blood cells are larger than normal and fail to function effectively.

Folic acid also plays a critical role in preventing neural tube defects and other birth defects, making testing crucial for pregnant women or those planning pregnancy. Individuals with cobalamin (Vitamin B12) deficiencies, neuropathy, or conditions like Crohn’s disease and celiac disease, which impair nutrient absorption, might also require this test.

Testing folate levels helps evaluate overall nutritional status and can uncover underlying causes of malnutrition or chronic health issues affecting red blood cells. Folate levels are measured using serum or plasma samples, which provide insight into immediate or longer-term folate levels, respectively.  

Test Preparation

Proper preparation ensures accurate test results. Patients are often advised to fast for several hours before the test, as recent food intake can affect folate measurements.

  • Medications and Supplements: Inform your doctor about any prescription drugs, over-the-counter medications, or supplements you are taking, as some substances can interfere with results.
  • Lifestyle Considerations: Avoid alcohol, illegal drugs, and certain herbs before the test, as these can influence folate absorption.
  • Pregnancy and Birth Defects: For pregnant women, testing is critical to prevent neural tube defects. Ensure your healthcare provider is aware of your pregnancy status.  

Test Procedure

The folate blood test is a simple procedure involving the collection of a small blood sample. A healthcare professional cleans the skin, inserts a needle, and draws blood into a tube. The sample is then sent to a laboratory to measure the folate concentration in the serum or red blood cells.

This test may also be performed alongside measurements of homocysteine levels to assess folate metabolism. Elevated homocysteine can indicate inadequate folate, affecting health outcomes such as birth defect prevention and cardiovascular health.  

Understanding Results

Folate test results typically fall into one of three categories: normal, low, or high.

  • Low Folate Levels: Often caused by conditions like celiac disease, Crohn’s disease, or dietary deficiencies. It may lead to folate deficiency anemia, characterized by fatigue, pale skin, and poor concentration. A low folate level is generally considered to be less than two nanograms per milliliter (ng/mL) in serum.
  • High Folate Levels: Rare but may result from excessive folic acid supplements or certain health conditions like liver disease or kidney dysfunction. A high level of folate in the blood is generally considered to be above 17.5 nanograms per milliliter (ng/mL).
  • Normal Levels: Indicate adequate dietary intake and absorption. A normal folate level in the blood is 2.7 to 17.0 nanograms per milliliter (ng/mL).

Abnormal results may warrant further tests or interventions, including dietary changes or folic acid therapy. 

Factors Affecting Results

Numerous factors can influence the outcomes of a folate blood test:

  • Diet and Nutrition: Poor dietary intake or nutrition absorption problems can lead to inaccurate results.
  • Medical Conditions: Disorders like celiac disease, Crohn’s disease, and other malabsorption syndromes affect folate absorption.
  • Medications: Certain drugs impact folate metabolism, which might skew results.
  • Nerve Tissues and Red Blood Cells: Conditions affecting these tissues may require additional investigation.  

Alternative Test Names

Folate blood tests may be referred to by various names, such as:

  • Vitamin B9 Test
  • Folic Acid Test
  • Pteroyl Glutamic Acid Test
  • Tetrahydrofolate Test

These alternative names highlight different facets of folate’s biological importance, such as its role in glutamate residues and one-carbon group metabolism.

Associated Risks

Though generally safe, a folate blood test carries minor risks, such as bruising or infection at the puncture site. Blood draws may be slightly more complicated for individuals with specific health conditions, such as megaloblastic anemia, kidney failure, or nerve damage.

Folate levels also correlate with long-term health risks, including brain or spine defects in newborns if deficiencies are left untreated.

Complementary Tests

To gain a comprehensive picture of health, folate tests are often paired with:

  • RBC Folate Testing: Measures folate stored in red blood cells.
  • Vitamin B12 Testing: To rule out cobalamin deficiency.
  • Pathology Tests: For conditions like malabsorption or neural tube defects.  

PART II: The Vitamin B12 Blood Test

Vitamin B12

Purpose of the Vitamin B12 Test

Vitamin B12 is essential for red blood cell production, nerve health, and tissue repair. A Vitamin B12 blood test helps diagnose deficiencies that may result in megaloblastic anemia or pernicious anemia, a condition caused by the lack of Intrinsic Factor (IP), which is crucial for Vitamin B12 absorption.

Other indications include assessing symptoms of neuropathy, digestive issues, or conditions like liver disease, which can alter B12 levels.

Testing is especially critical for those on vegan or vegetarian diets, as plant-based foods lack natural B12. 

Test Procedure and Preparation

Vitamin B12 tests are performed similarly to folate tests, requiring a blood draw. In certain cases, urine tests may also be used to assess methylmalonic acid (MMA) levels, which indicate B12 deficiency.

To prepare for the test:

  • Fasting: Avoid eating for 6–12 hours before the test.
  • Medications and Supplements: Discuss with your doctor if you’re taking proton pump inhibitors or H2 blockers, as these may affect results.
  • Lifestyle: Inform your healthcare provider of any dietary habits or symptoms, such as weakness, numbness, or a sore tongue.  

Interpreting Test Results

Normal values range from 160 to 950 picograms per milliliter (pg/mL) or 118 to 701 picomoles per liter (pmol/L). Low levels – below 200 pg/mL – may indicate conditions such as pernicious anemia, absorption issues, or dietary deficiencies.

While less common, high levels could suggest liver dysfunction, leukemia, or excessive supplementation.

Early detection of abnormal levels allows for timely intervention, including dietary changes or supplements.

Dietary Sources and Recommendations

To maintain adequate levels, include foods like:

  • Animal Products: Meat, fish, dairy, and eggs are rich sources of B12.
  • Fortified Foods: Cereals, plant-based milks, and nutritional yeast fortified with B12.
  • Supplements: Recommended for vegans, vegetarians, and older adults.

The recommended daily allowance (RDA) for adults is 2.4 micrograms, which increases during pregnancy and lactation.

Symptoms of Deficiency

Deficiency in Vitamin B12 can manifest in several ways, including:

  • Cognitive issues such as memory loss or confusion.
  • Fatigue, weakness, and difficulty walking.
  • Mouth soreness and swollen tongue.

Treatment Options for Abnormal Levels

Treatment depends on the cause and severity of deficiency:

  • Dietary Adjustments: Increasing intake of B12-rich foods.
  • Supplements and Injections: For severe deficiencies or absorption issues.
  • Addressing Underlying Conditions: Treating pernicious anemia, liver disease, or digestive disorders.

Vitamin B12 therapy is tailored to individual needs for effective results.

Risks and Sensations During the Test

Vitamin B12 blood tests are minimally invasive procedures with very few risks. However, understanding what to expect during and after the test can help alleviate any concerns.

During the procedure, a healthcare professional inserts a sterile needle into a vein, typically in the arm, to draw blood. While most people experience only a mild pinch or pressure, others may notice slight bruising, soreness, or tenderness at the puncture site.

Risks may be heightened for individuals with underlying health conditions. For example, individuals who have undergone gastric bypass surgery often require regular Vitamin B12 testing, as this procedure can significantly impair nutrient absorption, leading to long-term deficiencies. Left untreated, such deficiencies may result in neurological symptoms, including numbness, tingling, and loss of balance.

Over time, these issues could escalate into movement problems or even permanent nervous system damage.

Vitamin B12 deficiency can also manifest as weakness, a sore mouth or tongue, and delayed development in children.

Although rare, prolonged deficiency may increase the risk of brain damage due to compromised nerve function. Early detection and treatment are critical for preventing severe complications. If you feel lightheaded or anxious during blood draws, informing the technician can help ensure your comfort and safety throughout the process.

FAQs and Additional Considerations

Vitamin B12 testing often raises important questions, particularly for those at risk of deficiency or related health conditions. Below, we address some common concerns:

What causes Vitamin B12 deficiency?

A variety of factors can contribute to Vitamin B12 deficiency. Pernicious anemia, an autoimmune condition, prevents the body from absorbing B12 due to a lack of Intrinsic Factor (IF) in the stomach. Celiac disease and other gastrointestinal conditions also impede nutrient absorption. For vegans and vegetarians, dietary limitations can lead to insufficient B12 intake, as it is predominantly found in animal-based foods.

Can high levels of Vitamin B12 be harmful?

High levels are less common and typically stem from underlying medical conditions, such as liver disease, leukemia, or systemic lupus erythematosus (SLE). While excessive dietary intake is rare, abnormally high Vitamin B12 levels warrant further investigation to identify any associated disorders.

Who is at greater risk of deficiency?

Older adults face an increased risk due to diminished stomach acid production, which is necessary for B12 absorption. Additionally, individuals who have had gastric bypass surgery are prone to deficiencies because the altered digestive system interferes with nutrient uptake.

What is the relationship between Vitamin B12 and homocysteine?

Vitamin B12 plays a vital role in regulating homocysteine levels. Elevated homocysteine is a marker for cardiovascular risk and may also indicate B12 deficiency. Testing for both can provide a more comprehensive picture of health.

What are the symptoms of Vitamin B12 deficiency?

Common symptoms include fatigue, anemia, neurological issues like numbness and tingling, and difficulty concentrating. Long-term deficiencies may result in severe complications, such as nerve damage or cognitive decline.

For those concerned about deficiency risks, especially vegans, vegetarians, and individuals with autoimmune or digestive disorders, regular Vitamin B12 testing is a proactive step toward maintaining optimal health.

Where to Get Quick and Affordable Folate and Vitamin B12 Testing in Portland 🤓

A white van with the Smart Labs Now logo speeds down the highway.

If you’re in Portland, schedule testing with us for a quick, affordable, and gentle blood draw experience. All our tests, including our Vitamin Deficiency (Folate & B12 Levels) panel, are tuned for highly accurate results. 


Please consult your primary care physician before engaging with any pharmaceutical, natural substances, or activity regimens mentioned or prescribed in this post. Smart Labs Now is not responsible for health or life outcomes based on the information or recommendations provided. This account does not serve as a substitute for professional medical advice/help.

    Comments are closed