An elevated folate level on a blood test indicates a higher-than-normal concentration of Vitamin B9 in the bloodstream. Folate is the naturally occurring, water-soluble B vitamin found in foods like leafy greens and legumes. Folic acid is the synthetic version, commonly added to fortified foods and supplements. Vitamin B9 supports rapid cell division, DNA synthesis, and the formation of red blood cells. While adequate intake is necessary, an unexpectedly high reading warrants further investigation.
Defining High Folate Results
Folate status is typically assessed using two distinct measurements: serum folate and red blood cell (RBC) folate. Serum folate reflects recent dietary intake and supplement use, meaning its level can temporarily spike shortly after consuming a large meal or a supplement. A healthy adult serum folate level is generally considered to be above 4 nanograms per milliliter (ng/mL), but a reading significantly above the upper limit of the normal range, which can be around 17 ng/mL, is considered elevated.
The red blood cell (RBC) folate level offers a more accurate picture of the body’s long-term storage and tissue status of the vitamin. The adult RBC folate reference range is typically between 140 to 628 ng/mL, though this can vary by laboratory. A persistently high RBC folate level is a more significant finding, as it is less influenced by day-to-day variations in diet and suggests a long-term pattern of high intake or a problem with how the body is using the vitamin.
Common Causes of Elevated Folate
The most frequent reason for an elevated folate reading is consuming synthetic folic acid in excess of the body’s needs. This is largely driven by the widespread use of dietary supplements, such as multivitamins or B-complex formulas, which often contain high doses. Since folic acid is water-soluble, the body typically excretes excess amounts. However, high intake can overwhelm the liver’s capacity to process it, leading to a buildup of unmetabolized folic acid in the bloodstream.
Another major source is the consumption of fortified foods, including breakfast cereals, bread, rice, and pasta, to which folic acid is added. Combining high-dose supplementation with a diet rich in these fortified products can make the total daily intake quite high, increasing the likelihood of an elevated test result. While consuming naturally folate-rich foods could contribute, it is a less common cause of extreme elevation than the synthetic form. Genetic variations in the MTHFR gene can also slow the conversion of folic acid into its active form, potentially contributing to accumulation.
The Critical Interaction: Folate and Vitamin B12
An elevated folate level is a significant clinical concern because it can mask an underlying Vitamin B12 deficiency. Folate and Vitamin B12 work together to create DNA and mature red blood cells. A deficiency in either vitamin can cause megaloblastic anemia, characterized by abnormally large red blood cells.
If a person with an undiagnosed B12 deficiency takes high doses of folic acid, the excess folate can temporarily correct the blood issue, resolving the megaloblastic anemia. This correction removes the most common symptom that would prompt investigation, effectively masking the problem. However, the high folate level does nothing to prevent the progression of neurological damage caused by the lack of B12.
Vitamin B12 is required for the health of the nervous system, particularly for maintaining myelin, the protective sheath around nerve fibers. Without sufficient B12, this myelin can be damaged, leading to progressive and potentially irreversible neurological problems. Symptoms of nerve damage, such as numbness, tingling (peripheral neuropathy), memory loss, and balance problems, can worsen silently while the blood count appears normal. The risk of irreversible damage makes simultaneous testing of both B12 and folate levels a common practice.
Medical Management and Follow-Up
A high folate result should prompt a discussion with a healthcare provider to determine the cause and next steps. The first action involves reviewing all dietary and supplemental intake to identify and potentially reduce sources of synthetic folic acid. This may mean reducing or temporarily stopping the use of multivitamins or B-complex supplements.
Due to the masking concern, the immediate follow-up step is to confirm the status of Vitamin B12, even if the patient shows no signs of anemia. Additional testing for B12, and sometimes for metabolic markers like methylmalonic acid (MMA), is necessary to rule out a hidden deficiency that could cause neurological harm.
For individuals with certain genetic variants like MTHFR, their provider may suggest switching from synthetic folic acid to an active form, such as L-methylfolate (5-MTHF). This active form bypasses the need for the body to convert it, which may help reduce the accumulation of unmetabolized folic acid. Any change in supplementation should only be made under medical guidance, as high folate levels require professional assessment.