vitamin B9

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Related to vitamin B9: vitamin C, vitamin B12

vitamin B9


Synonym/acronym: Folic acid, vitamin B9.

Common use

To assist in evaluation of diagnoses that are related to fluctuations in folate levels such as vitamin B12 deficiency and malabsorption.


Serum (1 mL) collected in a gold-, red-, or red/gray-top tube.

Normal findings

(Method: Immunochemiluminometric assay [ICMA])
Conventional UnitsSI Units (Conventional Units × 2.265)
NormalGreater than 5.4 ng/mLGreater than 12.2 nmol/L
Intermediate3.4–5.4 ng/mL7.7–12.2 nmol/L
DeficientLess than 3.4 ng/mLLess than 7.7 nmol/L
Values may be slightly decreased in older adults due to the effects of medications and the presence of multiple chronic or acute diseases with or without muted symptoms.


Folate, a water-soluble vitamin, is produced by bacteria in the intestines and stored in small amounts in the liver. Dietary folate is absorbed through the intestinal mucosa and stored in the liver. Folate is necessary for normal red blood cell (RBC) and white blood cell function, DNA replication, and cell division. Folate levels are often measured in association with serum vitamin B12 determinations because vitamin B12 is required for folate to enter tissue cells. Folate is an essential coenzyme in the conversion of homocysteine to methionine. Hyperhomocysteinemia resulting from folate deficiency in pregnant women is believed to increase the risk of neural tube defects. Hyperhomocyteinemia related to low folic acid levels is also associated with increased risk for cardiovascular disease.

This procedure is contraindicated for



  • Assist in the diagnosis of megaloblastic anemia resulting from deficient folate intake or increased folate requirements, such as in pregnancy and hemolytic anemia
  • Monitor the effects of prolonged parenteral nutrition
  • Monitor response to disorders that may lead to folate deficiency or decreased absorption and storage

Potential diagnosis

Increased in

  • Blind loop syndrome (related to malabsorption in a segment of the intestine due to competition for absorption of folate produced by bacterial overgrowth)
  • Excessive dietary intake of folate or folate supplements
  • Pernicious anemia (related to inadequate levels of vitamin B12, due to impaired absorption, resulting in increased circulating folate levels)
  • Vitamin B12 deficiency (related to vitamin B12 levels inadequate to metabolize folate, resulting in increased circulating folate levels)

Decreased in

    Chronic alcoholism (related to insufficient intake combined with malabsorption) Crohn’s disease (related to malabsorption) Exfoliative dermatitis (related to increased demand) Hemolytic anemias (related to increased demand due to shortened RBC life span caused by folate deficiency) Liver disease (related to increased excretion) Malnutrition (related to insufficient intake) Megaloblastic anemia (related to folate deficiency, which affects development of RBCs and results in anemia) Myelofibrosis (related to increased demand) Neoplasms (related to increased demand) Pregnancy (related to increased demand possibly combined with insufficient dietary intake) Regional enteritis (related to malabsorption) Scurvy (related to insufficient intake) Sideroblastic anemias (evidenced by an acquired anemia resulting from folate deficiency; iron enters and accumulates in the RBCs but cannot become incorporated in hemoglobin) Sprue (related to malabsorption) Ulcerative colitis (related to malabsorption) Whipple’s disease (related to malabsorption)

Critical findings


Interfering factors

  • Drugs that may decrease folate levels include aminopterin, ampicillin, antacids, anticonvulsants, barbiturates, chloramphenicol, chloroguanide, erythromycin, ethanol, glutethimide, lincomycin, metformin, methotrexate, nitrofurans, oral contraceptives, penicillin, pentamidine, phenytoin, pyrimethamine, tetracycline, and triamterene.
  • Hemolysis may falsely increase folate levels.

Nursing Implications and Procedure

Potential nursing problems

ProblemSigns & SymptomsInterventions
Confusion; altered sensory perception (Related to hepatic disease and encephalopathy; acute alcohol consumption; hepatic metabolic insufficiency)Disorganized thinking, restless, irritable, altered concentration and attention span, changeable mental function over the day, hallucinations; altered attention span; unable to follow directions; disoriented to person, place, time, and purpose; inappropriate affectTreat the medical condition; evaluate medications; prevent falls and injury through appropriate use of postural support, bed alarm, or restraints; consider pharmacological interventions; record accurate intake and output to assess fluid status; monitor blood ammonia level; monitor and trend electrolytes; determine last alcohol use; assess for symptoms of hepatic encephalopathy; assess for sleep disturbances, incoherence; protect from physical harm; administer prescribed medication, blood, blood products to treat disease
Fatigue (Related to hepatic disease process; malnutrition; anemia; chemotherapy; radiation therapy)Decreased concentration; increased physical complaints; unable to restore energy with sleep; reports being tired; unable to maintain normal routineAssess for physical cause of fatigue; pace activities to preserve energy stores; rate fatigue on a numeric scale to trend degree of fatigue over time; identify what aggravates and decreases fatigue; assess for related emotional factors such as depression; evaluate current medications in relation to fatigue; assess for physiologic factors such as anemia
Nutrition (Related to poor eating habits; excessive alcohol use; altered liver function; nausea; vomiting)Known inadequate caloric intake; weight loss; muscle wasting in arms and legs; stool that is pale or gray colored; skin that is flaky with loss of elasticityDocument food intake with possible calorie count; assess barriers to eating; consider using a food diary; monitor continued alcohol use as it is a barrier to adequate nutrition; monitor glucose levels; monitor daily weight; provide dietary consult with assessment of cultural food selections; administer multivitamin as prescribed; provide parenteral and enteral nutrition as needed; assess liver function tests ALT, AST, ALP, glucose, protein, albumin, bilirubin, folic acid, thiamine, electrolytes
Gas exchange (Related to deficient oxygen capacity of the blood)Irregular breathing pattern, use of accessory muscles; altered chest excursion; adventitious breath sounds (crackles, rhonchi, wheezes, diminished breath sounds); signs of hypoxia; altered blood gas results; confusion; lethargy; cyanosisMonitor respiratory rate and effort based on assessment of patient condition; assess lung sounds frequently; use pulse oximetry to monitor oxygen saturation; collaborate with physician to administer oxygen as needed; elevate the head of the bed 30 degrees or higher; monitor IV fluids and avoid aggressive fluid resuscitation; assess level of consciousness; anticipate the need for possible intubation


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in detecting folate deficiency and monitoring folate therapy.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s gastrointestinal and hematopoietic systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture. Protect the specimen from light.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Nutritional Considerations: Instruct the folate-deficient patient (especially pregnant women), as appropriate, to eat foods rich in folate, such as liver, salmon, eggs, asparagus, green leafy vegetables, broccoli, sweet potatoes, beans, and whole wheat.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.
  • Patient Education

    • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP.
    • Answer any questions or address any concerns voiced by the patient or family.
    • Educate the patient regarding access to nutritional counseling services.
    • Provide contact information, if desired, for the Institute of Medicine of the National Academies (
  • Expected Patient Outcomes

    • Knowledge
    • Verbalizes understanding of the importance of reporting any difficulty breathing to facilitate timely interventions
    • States understanding of information provided to support lifestyle changes that will be necessary to manage disease process
    • Skills
    • Designs a dietary strategy that encompasses the concept of six small meals a day to better manage caloric needs
    • Describes ways to conserve energy and prevent fatigue
    • Attitude
    • Complies with the request to abstain from alcohol use
    • Complies with the HCP recommendation of a dietary consult to assist in managing caloric needs appropriately

Related Monographs

  • Related tests include antibodies antithyroglobulin, biopsy intestinal, capsule endoscopy, CBC, CBC RBC indices, complete blood count, RBC morphology, complete blood count, WBC count and differential, eosinophil count, fecal analysis, gastric acid emptying scan, gastric acid stimulation test, gastrin, G6PD, hemosiderin, homocysteine, intrinsic factor antibodies, thyroid, and vitamin B12.
  • Refer to the Gastrointestinal and Hematopoietic systems tables at the end of the book for related tests by body system.
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