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Folic acid in the blood
Last reviewed: 05.07.2025
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Reference values (norm) of folic acid concentration in adults: in blood serum - 7-45 nmol/l (3-20 ng/ml); in erythrocytes - 376-1450 nmol/l (166-640 ng/ml).
Folic acid is a water-soluble B vitamin and is a pteridine derivative. The human body is provided with folic acid due to its endogenous synthesis by intestinal microflora and consumption with food. In food, folic acid is present in the form of folic polyglutamate and other salts of folic acid (folates). The vitamin is absorbed after hydrolysis, reduction and methylation in the gastrointestinal tract. The average daily intake of folic acid is usually 500-700 mcg of folates per day. Of this amount, 50-200 mcg of folates are usually absorbed in the gastrointestinal tract, depending on metabolic needs (in pregnant women up to 300-400 mcg). In the body, folic acid is reduced to tetrahydrofolic acid (this requires the presence of vitamin B 12 ), which is a coenzyme involved in various metabolic processes. Typically, 5-20 mg (up to 75%) of folates are stored in the liver and other tissues. Folates are excreted in urine and feces and are also metabolized, so their serum concentrations decline within a few days after dietary intake ceases.
The main sources of folates for humans are yeast, cabbage, carrots, tomatoes, mushrooms, lettuce, spinach, onions, liver, kidneys, egg yolk, and cheese. The daily requirement of an adult for folic acid is 0.2 mg. It increases during pregnancy, breastfeeding, heavy physical labor, lack of protein in the diet, and intake of large doses of vitamin C (2 g or more).
The presence of mobile hydrogen atoms in the molecules of the active metabolite of folic acid - tetrahydrofolate - determines its participation as a donor in a number of oxidation-reduction reactions. It takes part in the synthesis of purines, pyrimidines, methionine, interconversions of serine and glycine, thereby regulating protein metabolism. Folates are necessary to maintain normal erythropoiesis, synthesis of nucleoproteins, cell proliferation, blood clotting, and prevention of atherosclerosis.
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