If there is no response, it is likely that the patient is not B12 deficient and other causes of the clinical problem must be sought. We use cookies to provide you with a better service. Department of Haematology Notes Vitamin B12 and serum folate are no longer performed on elderly patients in the acute setting unless there is a specific indication e. This test will not be repeated if it has been carried out within the last 3 months.
This test can be added on to a patient request if the laboratory has an appropriate sample that is less than 3 days old. Turnaround Times 3 working days from request Reference Ranges. Please note: The reference ranges provided are for adults.
Reference ranges for infants and children are dependant on age. Results should be interpreted along with clinical features and other laboratory results. B12 levels fall physiologically in pregnancy and this usually does not represent deficiency at a biochemical level.
If the mother has otherwise unexplained anaemia or has other clinical signs of B12 deficiency , consider a treatment trial of B12 replacement as suggested below following local standard advice for non-pregnant individuals with low serum B12 values. Check intrinsic factor antibody status before B12 treatment. Prescribe parenteral B12 1mg x 5 over 2 weeks. In humans, it is obtained only from animal proteins and requires intrinsic factor IF for absorption. The body uses its vitamin B12 stores very economically, reabsorbing vitamin B12 from the ileum and returning it to the liver; very little is excreted.
Vitamin B12 deficiency may be due to lack of IF secretion by gastric mucosa eg, gastrectomy, gastric atrophy or intestinal malabsorption eg, ileal resection, small intestinal diseases. Vitamin B12 deficiency frequently causes macrocytic anemia, glossitis, peripheral neuropathy, weakness, hyperreflexia, ataxia, loss of proprioception, poor coordination, and affective behavioral changes.
These manifestations may occur in any combination; many patients have the neurologic defects without macrocytic anemia. Pernicious anemia is a macrocytic anemia caused by vitamin B12 deficiency that is due to a lack of IF secretion by gastric mucosa.
Serum methylmalonic acid and homocysteine levels are also elevated in vitamin B12 deficiency states. For specimens without antibodies and the patient is symptomatic, follow-up testing for vitamin B12 tissue deficiency may be indicated.
However, the test is not specific, and many situations can cause an increased level. In patients being evaluated for vitamin B12 deficiency who have intrinsic factor blocking antibodies IFBA , false elevations of vitamin B12 may occur due to IFBA interference, potentially obscuring a physiological deficiency of vitamin B Patients who have received a vitamin B12 injection or radiolabeled vitamin B12 injection within the previous 2 weeks may have high serum vitamin B12 levels, which can interfere with this assay leading to falsely elevated results.
Many other conditions are known to cause an increase or decrease in the serum vitamin B12 concentration and should be considered in the interpretation of the assay results, including:. The evaluation of macrocytic anemia requires measurement of both vitamin B12 and folate levels; ideally, they should be measured simultaneously.
A doubling in MMA from 0. B12 deficiency can temporarily cause dementia in the elderly. Those who at least partially improved had mild dementia for less than 2 years [ 90 ].
Vitamin B12 deficiency can impair motor function e. In 90 patients with early type 2 diabetes, those on metformin had lower B12 levels and were more prone to nerve pain peripheral neuropathy [ 98 ]. Supplementation helped even when the nerve pain was caused by issues other than vitamin B12 deficiency [ 99 ].
In a study of 2, adults, those with low B12 levels had lower bone mineral density [ ]. In a study of frail elderly, osteoporosis occurred more often among women with marginal or deficient B12 status. No association was found in men [ ]. Vitamin Bdeficiency may increase the risk of cancer by impairing DNA synthesis and repair [ , ]. In a large study of smokers almost 30, people , lower initial vitamin B12 levels were associated with a 5.
Low-normal values were linked to a 3-fold increased risk [ ]. However, rather than being a contributing factor, in this case, low vitamin B12 may be a consequence of stomach inflammation , which precedes stomach cancer and decreases B12 absorption [ ]. Discuss the additional lifestyle changes listed below with your doctor.
None of these strategies should ever be done in place of what your doctor recommends or prescribes! Common sources of B12 include animal products such as red meat, fish, poultry, yogurt, and milk. Vitamin B12 is poorly absorbed from eggs [ 8 , 9 , ]. A couple of studies suggest that algae such as chlorella may also be a viable source of B12 [ ]. However, keep in mind that vitamin B12 levels are often low due to underlying conditions, such as impaired nutrient absorption due to gut-associated disease.
Alcohol consumption can reduce B Avoiding it will prevent further decreases in B12 levels [ 17 , 16 , 49 ]. Smoking nicotine can also lower B12 levels and should be avoided [ 57 ]. Knowing that your drugs likely decrease B12 levels can help if you take action and supplement accordingly.
Metformin in diabetics is a good example [ 98 ]. Review your medication with your doctor or another healthcare professional, and discuss alternatives for those that are decreasing your B12 levels. Natural or biologically active forms hydroxocobalamin, methylcobalamin, and adenosylcobalamin are a better option than synthetic cyanocobalamin. A study suggests that calcium supplements may improve B12 absorption in diabetics taking metformin [ ].
Blood tests for B12 may show elevated levels in people who are or have recently been taking vitamin B supplements [ ]. This is usually not of concern as vitamin B12 is not considered toxic. High levels of vitamin B12 when not supplementing are important because they may indicate an underlying health condition , such as:. Causes listed above are commonly associated with high vitamin B12 levels. However, much like the studies linking folic acid to cancer, the studies below are not conclusive.
Many point only to an association, not causation. More large-scale and well-designed research is needed. In a study of over , people without cancer, the risk of cancer increased with higher B12 levels and was highest during the first year of follow-up. The risk was particularly elevated for blood-, smoking-, and alcohol-related cancers [ ]. A large-scale study looked at 5, lung cancer-control pairs and reviewed genetic data of 29k cancer patients and 56k healthy people.
Higher blood vitamin B12 was associated with higher lung cancer risk. In addition, genetic variants linked to higher vitamin B12 levels were also linked with higher overall lung cancer risk [ ].
Two meta-analyses of 6 and 7 studies, respectively, linked higher vitamin B12 levels to a small increase in the risk of prostate cancer [ , ]. Several studies of hospitalized patients over 5, in total found a link between higher B12 levels and mortality [ , , , , ]. In over 25, cancer patients, those with high B12 levels had lower chances of surviving.
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