Lab Testing For Vitamin B12 & Folate Deficiencies

 The body needs two B complex vitamins – folate and B12 – for several crucial functions. For instance, the body uses these vitamins to make white blood cells, red blood cells, synthesize DNA, and repair cells and tissues. B12 is also critical for nerve cell function. 

Unfortunately, the body cannot produce folate (also known as vitamin B9 and folic acid), and B12 and the vitamins are only supplied by one’s diet. A healthy body should contain ample vitamin B12 stores to last 3 to 5 years. However, the body does not store a lot of folate vitamins. When one is diagnosed with folate and/or B12 deficiency, it denotes a chronic shortage of one, or in some worse case scenarios, both vitamins. 

In the United States, folate and B12 deficiencies are not common conditions that healthy adults face as the body can store the vitamins for some time. Typically, adults eat diets that contain the vitamins or are supplemented with these vitamins, thereby meeting their daily requirements.

However, some individuals are at risk of experiencing deficiency, including: 

  • The elderly 
  • Individuals with intestinal conditions and issues that prevent their digestive systems from absorbing enough of these two vitamins 
  • Pregnant women, as they need an increased amount of both vitamins 
  • Vegans and vegetarians 
  • Heavy alcohol drinkers 
  • Individuals living with long-term use of certain medicines  

B12 deficiency among the demographic of 60 and below is estimated to be approximately 6% in the United Kingdom and the United States. The B12 deficiency is estimated to be prevalent in more than 20% among individuals age 60 years and more. 

Folate and B12 deficiencies and their signs and symptoms can take anywhere from months to years before they manifest in adults. Children and infants tend to show signs of deficiency more rapidly as their tender years are not enough to allow them to accumulate enough stores. 

Over time, the deficiency in folate and/or B12 can give rise to the condition of enlarged red blood cells known as macrocytic anemia. The production of fewer and enlarged blood cells reduces the blood cells’ ability to transport oxygen from the lungs to the body. People suffering from anemia will experience short-breath, light-headedness, and weaknesses.  

Megaloblastic anemia, which is a type of macrocytic anemia that is associated with cellular changes to one’s bone marrow, aside from the production of enlarged and fewer red blood cells. This type of anemia is also characterized by a decrease in the production of white blood cells, platelets, and reticulocytes. 

A B12 deficiency can also cause varying degrees of nerve damage or neuropathy, which results in numbness and tingling sensation in a person’s feet and or hands. In some severe cases, mental changes are observed, resulting in irritability, confusion, or even dementia. 

Pregnancy demands an increased amount of folate for the proper development of fetus owing to the increased demands induced by rapidly developing fetal cells. Pregnancy-related folate deficiency, especially during the early weeks when many expectant mothers are oblivious of their pregnancies, can lead to premature births. In other cases, the deficiency can give rise to neural tube birth defects (NTDs), including spina bifida. 

The Food and Drug Administration mandates an increased supplementation of all numerous grain products as a measure to curb and prevent NTDs. This measure resulted in a 50% decrease in NTDs in the United States. Even with these efforts, getting the right amount of folate can be a daunting task. As such, pregnant women are recommended to take 400 micrograms of supplementing folate every day. 

Signs and Symptoms Deficiencies 

The onset of folate and B12 deficiencies gives rise to subtle and nonspecific signs and symptoms. Some of the signs are, in fact, the effects of nerve damage, megaloblastic anemia, and/or gastrointestinal changes.

The affected individuals might experience mild to severe signs and symptoms, which might include: 

  • Dizziness
  • Diarrhea
  • Loss of appetite 
  • Constipation
  • Muscle weakness 
  • Fatigue
  • Sore or smooth mouth and tongue
  • Pale skin
  • Irregular heartbeats
  • Shortness of breath 
  • Rapid heart rate
  • Confusion and/or forgetfulness 
  • Numbness, tingling, and/or burning in the arms, hands, feet, and legs (with B12 deficiency) 
  • Irritability
  • Paranoia


Folate and/or B12 deficiency has a variety of causes. Some of them are: 

  • Insufficient Dietary Intake 

B12 is mainly sourced from animal-based foods such as poultry, eggs, fish, meat, and milk. Foliate, also known as vitamin B9 or folic acid, is mainly sourced from leafy green veggies, dry beans, citrus fruits, vitamin-fortified cereals, and yeast. 

With the body being capable of storing vitamin B12 worth several years in the liver, and the fact that a variety of foods consumed in the U.S. are fortified with the vitamin, a dietary deficiency of the vitamin if relatively rare. However, it can occur among people with poor nutrition, malnourishment, vegans, and even breastfed infants of vegan mothers.  

In adults, a dietary deficiency does not yield to symptoms until the vitamin stores in the body are depleted. Deficiencies in infants and children can occur quickly since they have had little to no time to accumulate enough vitamin stores, as is the case in adults. 

Folate deficiencies were common in the past. However, since 1997 when the United States government mandated the fortification of bread, cereals, and other grain products with folic acid, folate deficiency cases dropped. Folate, a water-soluble vitamin, cannot be stored in the fat tissues. On average, the total amount of folate available in the body is 15 to 30 mg. Around half of it is stored in the liver, with the rest being stored in the blood as well as other tissues. Since folic acid is stored in small quantities, you should consume it much more regularly than B12. 

  • Malabsorption  

Both folate and B12 deficiencies can occur in people with conditions that negate the absorption of the vitamin in the small intestines. The intake of vitamin B12 occurs in a series of steps. First and foremost, the vitamin is broken down from protein by pepsin and stomach acid.  

In the next step, the vitamin is processed in the small intestine, where the vitamin binds with intrinsic factor (IF) to form the B12-IF complex. IF is a protein made by the parietal cells in the stomach. The B12-IF complex is absorbed in the small intestines, after which the transcobalamin’s “carrier proteins” bind the complex. The final step is entering into circulation. 

People who suffer from a disease that affects any of these steps will experience deficiencies as the absorption of B12 is impaired. 

Some of the conditions that can affect these steps are: 

  • Pernicious anemia – An Autoimmune disease that affects B12 absorption. The condition is the most common cause of B12 deficiency, and it affects the production of intrinsic factor. The IF is produced by the parietal cells that line the stomach. When one suffers from pernicious anemia, the inflammation can damage the cell, thereby affecting the production of IF. Consequently, this prevents the intestines from absorbing B12. With insufficient B12 absorption and low availability of the vitamin, the body produces fewer and enlarged red blood cells, which is termed as megaloblastic anemia, a type of macrocytic anemia. 
  • Celiac Disease – This is another autoimmune disease whereby the immune system produces an inappropriate response to the gluten, which is a protein found in rye, wheat, and barley. 
  • Inflammatory Bowel Disease – It includes ulcerative colitis and Crohn’s disease. 
  • Presence of parasites or bacterial overgrowth in the intestines 
  • A Reduction in Stomach Acid Production – Stomach acid is used to separate B12 from the source proteins. The reduction of stomach acid production is the most common cause of B12 deficiency among individuals using drugs such as proton pump inhibitors and H2 receptors antagonists as they suppress acid production. It is also a common cause among the old. 
  • Stomach Surgery – Any stomach surgery that removes part of the stomach and affects the parietal cells and or the intestines can reduce the absorption of B12. As such, undergoing a gastric by-pass can cause a B12 deficiency. 
  • Chronic Pancreatitis – Long-lasting pancreases inflammation, typically caused by long-term alcohol abuse of gallstones, can result in B12 deficiency.  

Increased Need for B12 and/or Folate 

Pregnancy increases DNA synthesis and cell production, which, in turn, increases the need for folate. It is recommended that women take prenatal vitamin supplements that include folic acid before getting pregnant and throughout the pregnancy to prevent some of the birth defects. Moreover, women planning to get pregnant should observe a proper die. Furthermore, they should consider taking supplements that ensure they meet the daily minimum recommended consumption of 400 mcg of folate.  

Keep in mind that neural tube defects can arise during the first weeks of pregnancy even before you realize you are pregnant. You can read more on this topic by reading the Neural Tube Defects article. Additionally, folate deficiency only intensifies with pregnancy. This can lead to neural tube defects and premature birth, as well. 

Individuals with chronic hemolytic anemia (including sickle cell anemia) or with cancer that has metastasized (spread) need more folate. 

Some anti-seizure medications, including phenytoin, can reduce folate by blocking its absorption. 

The anti-cancer drug Methotrexate affects the body’s use of folate and metabolism. 

Other Causes: 

Alcoholism or heavy alcohol drinking can cause folate and or B12 deficiencies owing to malabsorption, poor nutrition, and a decrease in the amount of B12 released from dietary proteins. 

Some prescription drugs can cause B12 deficiency. Metformin, a diabetes drug, blocks the absorption of B12. Omeprazole, which is an acid reflux drug, reduces the production of gastric acid, which prevents the release of B12 from the proteins one eats. 

A methylenetetrahydrofolate reductase gene (MTHFR) mutation impairs the function of folate. Approximately, 1% African Americans, 10% Caucasians, and 25% Hispanics, may have this mutation. 


B12 deficiency screening is not recommended unless a patient has high-risk factors. Lab testing can be used to detect vitamin deficiency and determine the level of severity and the underlying cause of symptoms. The test can also help monitor the effectiveness of the treatment.  

The Variety of Test That Can Diagnose and Or Monitor Folate and B12 Deficiencies: 

CBC – The complete blood count test is a group of tests that evaluate the health of one’s blood cells. 

CBC test determines the number of red blood cells, white blood cells, hematocrit, hemoglobin level, mean corpuscular volume (MCV, which is indicative of the RBC size), and platelet count. Megaloblastic anemia/Macrocytic anemia and enlarged RBC are associated with folate and B12 deficiency, which routine CBC can help identify. 

These tests can also help identify abnormal physical characteristics of the cells, thereby indicating of B12 and folate deficiencies. For instance, the deficiencies decrease platelets, RBCs, hemoglobin, hematocrit, and WBCs.  

B12 Blood Level – A low B12 blood level indicates a deficiency, although it does not determine the cause of the deficiency. Reasons for the deficiency can be IF production inhibition causing malabsorption. This test is also ordered to monitor treatment effectiveness.  

Folate Level – RBC folate level or serum is tested to determine the folate level. A low level is indicative of deficiency. This test is also ordered to monitor the effectiveness of treatment. You should note that come health officials and organizations do not recommend testing folate levels. Instead, they recommend treating the patient suffering from a deficiency with necessary supplements. 

Methylmalonic acid (MMA) – Generally, low B12 is associated with high MMA. An MMA test can help detect early or mild B12 deficiency.  

Homocysteine Test – Homocysteine tends to be elevated in instances of folate and B12 deficiency. 

Tests Used to Help Determine B12 Deficiency Causes 

Intrinsic Factor Antibody Test – The Intrinsic Factor antibody impedes the IF from functioning. It prevents the IF from carrying B12 or the B12 from being absorbed in the small intestines. 

Parietal Cell Antibody Test – This is an antibody that affects the parietal cells that make the IF. The antibody, which is present in a lot of people with pernicious anemia and other autoimmune diseases, can impede the production of intrinsic factor. 

Gastrin Test – This is a hormone that regulates the production of gastric acid during the digestive process. An increased level of gastrin is sometimes seen in people with pernicious anemia.