How does your body get rid of folate?

January 6, 2026 •

3 min read

Folate is a water-soluble B vitamin, meaning it is not stored in large quantities in the body, and therefore, leftover amounts are regularly cleared from the system. In fact, an adult typically needs to replenish their folate stores daily to prevent deficiency from a lack of consistent intake.

Quick Summary

The body eliminates excess folate primarily through urinary excretion, though the liver also plays a crucial recycling role through the enterohepatic cycle. Excess, especially from supplements, is rapidly flushed out through the kidneys and leaves the body in urine.

Key Points

Water-soluble Nature: Excess folate is easily eliminated through the urine because it is a water-soluble vitamin and not stored in fat cells.
Kidney Filtration: The kidneys are the main organ for clearing folate from the blood, filtering it out and then reabsorbing most of it to conserve body stores.
Urinary Excretion: With high folate intake, particularly from supplements, the kidney's reabsorption capacity is saturated, causing the excess to be excreted in the urine.
Enterohepatic Circulation: The liver recycles folate by releasing it into bile and then reabsorbing it in the intestine, a cycle that conserves the body's supply.
Catabolite Excretion: The body also eliminates metabolically degraded folate products, known as catabolites, in the urine.
Vitamin B12 Interaction: A deficiency in vitamin B12 can lead to the 'folate trap,' where folate is retained in a form that is then excessively excreted by the kidneys.
Liver Metabolism: The liver actively metabolizes and stores folate before distribution or elimination, and conditions affecting liver health can disrupt this process.

The Primary Elimination Route: Urinary Excretion

As a water-soluble vitamin, folate does not accumulate in the body's fatty tissues. The kidneys are the main regulators of fluid and electrolyte balance, and their filtering process is the primary way that excess folate leaves the body.

The Kidney's Filtering and Reabsorption Process

Glomerular Filtration: In the kidneys, blood is filtered through tiny structures called glomeruli. During this process, unbound or monoglutamate folate is filtered from the bloodstream into the renal tubules.
Proximal Tubule Reabsorption: In healthy individuals with normal folate levels, the majority of the filtered folate is efficiently reabsorbed back into the blood in the proximal tubules. This reabsorption is mediated by specific transporters, such as the folate receptor alpha (FRα) and the reduced folate carrier (RFC). This recycling mechanism helps conserve the body's folate supply, preventing unnecessary loss.
Urinary Excretion: When a person consumes high amounts of folate, particularly from supplements, the body's capacity for tubular reabsorption becomes saturated. This results in the excess folate being excreted in the urine. Studies have shown that with high oral doses of folic acid, a large percentage is recovered in the urine within 24 hours.

The Liver's Role and Enterohepatic Circulation

The liver plays a central role in folate metabolism and its distribution throughout the body. It takes up monoglutamate folate from the bloodstream via transporters and converts it into its more active, polyglutamate forms for storage and use in metabolic processes.

The Folate Enterohepatic Cycle

A significant portion of the body's folate is circulated between the liver and the intestines in a process known as the enterohepatic cycle.

The liver processes folate and stores it, primarily as polyglutamates.
When needed, the liver secretes processed folate into the bile.
The bile, containing folate, is released into the small intestine.
The folate is then mostly reabsorbed by the intestinal cells back into the blood, where it is either returned to the liver or distributed to other tissues.

This efficient cycle helps conserve folate and maintain stable systemic levels. However, certain conditions, like chronic alcoholism, can disrupt this cycle and cause increased biliary excretion of folate, leading to a loss of the vitamin.

Comparison of Folate and Folic Acid Elimination

There are key differences in how the body handles naturally occurring food folate and synthetic folic acid, primarily due to their different chemical forms. Natural folates are polyglutamates that need to be broken down before absorption, while synthetic folic acid is absorbed more readily.


Feature	Natural Food Folate	Synthetic Folic Acid
Absorption Rate	Approximately 50% bioavailability; requires enzymatic breakdown.	Approximately 85-100% bioavailability; does not require breakdown.
Metabolism	Primarily absorbed as 5-methyl-THF and transported directly to the liver.	Metabolized in the liver by dihydrofolate reductase (DHFR); high doses can exceed the liver's capacity, leading to unmetabolized folic acid in the bloodstream.
Excretion	Excess is excreted as breakdown products, like pABG and apABG.	Excess is excreted directly in the urine, especially at high doses.
Potential Issues	Deficiency due to poor diet or malabsorption.	Unmetabolized folic acid in the blood at high doses; can mask Vitamin B12 deficiency.

Other Factors Influencing Excretion

Folate Catabolism: The body metabolizes and breaks down some folate into catabolites, primarily para-acetamidobenzoylglutamate (apABG), which are then excreted in the urine. This represents a smaller, constant loss of folate reserves.
Vitamin B12 Deficiency: A lack of vitamin B12 can lead to a condition known as the 'folate trap'. This impairs the conversion of 5-methyl-THF back into its active form, leading to an accumulation of 5-methyl-THF in the serum that is eventually filtered and excreted by the kidneys.
Alcoholism: Chronic alcohol consumption can interfere with folate absorption and increase its urinary and biliary excretion, contributing significantly to folate deficiency.
Kidney Disease: Individuals undergoing kidney dialysis experience increased folate loss during the procedure, which can lead to deficiency.
Folate Antagonists: Certain medications, such as methotrexate, interfere with folate metabolism and promote its elimination.

Conclusion

In summary, the body disposes of excess folate primarily through the kidneys via urinary excretion, a process driven by its water-soluble nature. The liver and an efficient enterohepatic circulation system also play a key role in recycling folate to conserve the body's supply. While the body effectively manages normal intake, high supplemental doses can lead to increased excretion. A balanced understanding of these pathways highlights why a continuous dietary supply is necessary to maintain adequate folate levels. For further detailed reading on folate transport proteins in the kidneys, one can consult studies such as the review on renal conservation of folates.

Frequently Asked Questions

Folate is not stored in large quantities because it is a water-soluble vitamin. Unlike fat-soluble vitamins, any excess folate that the body doesn't need is simply passed through the urine instead of being stored for long periods.

The kidneys play a crucial role in maintaining folate balance. They filter folate from the blood, but most of it is then efficiently reabsorbed back into the bloodstream through specialized transporters to ensure the body doesn't lose too much.

The enterohepatic cycle is the process where the liver secretes folate into bile, which is then released into the small intestine. The folate is mostly reabsorbed back into the bloodstream, helping to conserve the body's stores.

Yes, taking high doses of folic acid, especially from supplements, can overwhelm the body's metabolic pathways. As a result, a larger proportion of the vitamin is excreted in the urine compared to lower, physiological doses.

Yes, several conditions can affect folate elimination. For example, chronic alcoholism can increase folate excretion in the bile, and kidney dialysis can lead to higher folate loss from the body.

Yes, the excretion can differ because natural folates and synthetic folic acid are handled differently by the body. Synthetic folic acid is absorbed more readily and can saturate metabolic processes at higher doses, leading to more direct urinary excretion.

Folate catabolites are the breakdown products of folate metabolism, such as para-acetamidobenzoylglutamate (apABG). These catabolites are also eliminated by the body, primarily through the urine.