Vitamin B12, also known as cobalamin, is an essential nutrient that plays a crucial role in many body functions. Vitamin B12 helps make DNA and red blood cells, keeps the nervous system functioning properly, and is involved in metabolizing food. Low levels of vitamin B12 can lead to anemia and nervous system problems.
Vitamin B12 levels can be tested through a simple blood test. This article will examine the Quest Diagnostics test codes used to order and bill for vitamin B12 lab tests. We’ll look at the various B12 lab test options, typical reference ranges for results, and reasons for testing B12 levels.
Quest Diagnostics Vitamin B12 Test Codes
Quest Diagnostics uses specific numeric codes to represent different lab tests. These codes are used internally by Quest for processing and billing tests. Patients typically do not need to know the codes, as the doctor’s office orders the tests by name. But for reference, the main Quest vitamin B12 test codes are:
| Test Name | Quest Code |
|---|---|
| Vitamin B12 | 44785 |
| Vitamin B12 & Folate | 37860 |
| Methylmalonic Acid | 85018 |
| Homocysteine | 17010 |
The basic vitamin B12 test checks current levels of cobalamin in the blood. Combination tests add on folate testing. Methylmalonic acid and homocysteine are functional tests that can provide additional information about vitamin B12 status.
Normal Vitamin B12 Levels
Quest Diagnostics provides the following reference range for standard blood tests of vitamin B12 levels in adults:
– Deficient: Less than 200 pg/mL
– Low: 200-400 pg/mL
– Normal: 401-914 pg/mL
– High: Greater than 914 pg/mL
The reference range can vary slightly between labs. Children tend to have higher levels than adults. Anything under 200 pg/mL indicates a true B12 deficiency. Borderline low levels between 200-400 pg/mL may suggest a mild deficiency, especially when symptoms are present.
Functional vitamin B12 tests like methylmalonic acid and homocysteine help shed more light on borderline cases. An elevated MMA or homocysteine in conjunction with low-normal B12 levels can confirm an elevated risk for deficiency.
Reasons for Vitamin B12 Testing
Doctors may order vitamin B12 testing for the following reasons:
1. Evaluate Anemia
Vitamin B12 deficiency is a common cause of macrocytic or megaloblastic anemia. This is characterized by larger-than-normal red blood cells. A vitamin B12 test is typically ordered when routine blood counts find abnormal mean corpuscular volume (MCV).
2. Assess Neurological Symptoms
Since B12 is vital for proper nerve function, B12 testing is done when patients have neurological symptoms possibly related to deficiency. This includes:
– Numbness or tingling in hands and feet
– Difficulty walking or loss of balance
– Memory problems or cognitive decline
– Depression, irritability, or dementia
– Vision changes or eye twitching
3. Check for Causes of Malabsorption
Certain gastrointestinal disorders interfere with B12 absorption and increase deficiency risk. Doctors may order B12 testing for patients with:
– Pernicious anemia (autoimmune disorder)
– Gastric bypass or removal of parts of intestine
– Crohn’s disease
– Celiac disease
– Pancreatic insufficiency
4. Monitor Treatment Response
Vitamin B12 levels are measured before and after treatment for deficiency. This helps determine if supplementation is increasing B12 levels into the normal range.
5. Assess Dietary Intake
Since B12 comes from animal foods, strict vegetarians and vegans are at higher risk of deficiency. B12 levels can help assess dietary intake adequacy.
Interpreting Vitamin B12 Test Results
Low vitamin B12 levels typically prompt treatment with B12 injections or high-dose oral supplements. Normal or high levels are generally reassuring. However, it’s important to interpret B12 test results in the context of the patient’s health history and risk factors.
Some key points for analysis include:
- Symptoms – Are symptoms consistent with B12 deficiency present?
- Supplements – Is the patient taking B12 supplements that could falsely elevate results?
- Diet – Does the patient eat a strict vegetarian/vegan diet?
- Medications – Are medications known to impact B12 being taken?
- Other conditions – Is there presence of pernicious anemia, celiac disease, etc.?
- Retesting – Should functional B12 tests be ordered for borderline results?
Thorough clinical evaluation combined with intelligently selected B12 lab testing provides the best information for vitamin B12 status assessment and appropriate treatment.
Vitamin B12 Test Methodology
There are two main methods used for measuring vitamin B12:
1. Immunoassay
Immunoassays use the principle of antibodies binding to B12 molecules in the blood sample. This allows detection and quantification of B12. The most common type of immunoassay used is chemiluminescence, which produces light signals proportional to the amount of B12 present.
Advantages of immunoassays:
– Relatively fast and inexpensive
– Automated on clinical chemistry analyzers
Disadvantages:
– Can have interference from B12 analogues
– Less accurate at low levels
2. LC-MS/MS
LC-MS/MS stands for liquid chromatography-tandem mass spectrometry. This method uses chromatography to separate B12 from other compounds. Then two rounds of mass spectrometry precisely identify and quantify B12.
Advantages of LC-MS/MS:
– Very sensitive and specific for active B12
– Low interference from binding proteins
– Accurate at low concentrations
Disadvantages:
– Expensive equipment required
– Slower testing time
– Unavailable in many laboratories
Most labs use automated immunoassays due to lower costs. But when accuracy is critical at low B12 levels, LC-MS/MS is considered the gold standard. Quest offers both testing methodologies.
Food Sources of Vitamin B12
Since vitamin B12 is primarily found in foods of animal origin, deficiency is more likely in vegetarians and vegans. Here are good dietary sources of B12:
| Food | Serving | B12 Amount |
|---|---|---|
| Beef liver | 3 ounces | over 100 mcg |
| Sardines | 3 ounces | ~9 mcg |
| Salmon | 3 ounces | ~5 mcg |
| Tuna | 3 ounces | ~3 mcg |
| Eggs | 1 large | ~0.6 mcg |
| Milk | 1 cup | ~0.9 mcg |
| Yogurt | 1 container | ~1.4 mcg |
| Cheese | 1 ounce | ~0.4 mcg |
The recommended daily intake of B12 is around 2.4 mcg. This can be easily achieved by including animal foods like meat, fish, eggs and dairy. Supplements are another option to prevent deficiency in those with restricted diets.
Supplements and Medical Treatment
Vitamin B12 supplements are used both for prevention and treatment of deficiency. Supplement types include:
– Tablets – Inexpensive but only 1-2% absorbed
– Sublingual – Dissolve under tongue for better absorption
– Nasal gels/sprays – Absorbed through mucous membranes
For diagnosed B12 deficiency, medical treatment with vitamin B12 injections almost always needed. This allows full doses to be administered and absorbed.
– Hydroxocobalamin – Most commonly prescribed injectable form
– Cyanocobalamin – Cheaper but not always well absorbed
Loading doses are given intramuscularly once weekly for 1-2 months to replenish body stores. Maintenance shots are then continued at longer intervals determined by the patient’s needs and response. Lifelong injections may be required in pernicious anemia cases.
Causes of Vitamin B12 Deficiency
Some key causes and risk factors for vitamin B12 deficiency include:
Dietary Causes
- Vegan or vegetarian diets
- Malabsorption from gastric bypass surgery
- Long term use of heartburn medications
- Alcoholism
Medical Causes
- Pernicious anemia (autoimmune)
- Celiac or Crohn’s disease
- Pancreatic insufficiency
- Removal of parts of stomach or intestine
- HIV/AIDS
- Other nutrient malabsorption disorders
Medications
- Proton pump inhibitors like omeprazole
- Histamine H2 blockers like ranitidine
- Metformin
- Certain anticonvulsants
Risk increases with age due to decreased stomach acid production needed for B12 absorption from foods. Strict vegetarians should take supplements or eat fortified foods to prevent deficiency.
Health Complications of Vitamin B12 Deficiency
If left untreated, vitamin B12 deficiency can lead to the following complications and conditions:
Hematological
- Megaloblastic or pernicious anemia
- Elevated MCV
- Abnormal red blood cell morphology
- Reduced white blood cell count
- Mild thrombocytopenia
Neuropsychiatric
- Numbness/tingling of extremities
- Gait abnormalities
- Cognitive changes and memory loss
- Depression
- Dementia
- Psychosis
Gastrointestinal
- Glossitis (inflamed tongue)
- Constipation
- Loss of appetite
- Nausea
- Weight loss
Other
- Weakness and fatigue
- Vision changes
- Pale skin
- Poor growth in children
- Birth defects
Early treatment with B12 injections and dietary correction helps resolve symptoms and prevent permanent neurological damage.
Conclusion
Vitamin B12 deficiency is common but can often go undetected in early stages. Vitamin B12 testing is important for identifying deficiency and guiding treatment decisions. Quest Diagnostics offers accurate vitamin B12 lab testing using immunoassay and LC-MS/MS methods. Patients with B12 deficiency symptoms, macrocytic anemia, neurologic disorders, digestive issues, or risk factors like vegetarian diets should have B12 levels checked. Prompt treatment helps reverse deficiency and avoid complications. Ongoing monitoring ensures adequate levels are maintained through supplements or lifestyle adjustments.