How fast does vitamin C go through your body?: Understanding Absorption and Excretion

October 13, 2025 •

5 min read

As a water-soluble nutrient, excess vitamin C is not stored in the body and is primarily excreted in the urine within 24 hours. How fast does vitamin C go through your body? The speed and efficiency of this process are highly dependent on the dose, individual health, and whether the vitamin is from food or a supplement.

Quick Summary

The speed at which vitamin C is processed depends largely on intake levels. Excess is rapidly eliminated by the kidneys, while absorbed vitamin C can remain in tissues for weeks. Higher doses result in lower absorption efficiency and quicker excretion.

Key Points

Dose Matters: At low, dietary levels (30–180mg), vitamin C absorption is highly efficient (70-90%), but it drops below 50% for high doses (>1g).
Bloodstream vs. Tissues: The plasma concentration of vitamin C has a short half-life of 30 minutes to 2 hours, but tissue stores deplete much more slowly with a whole-body half-life of 10–20 days.
Excretion is Rapid for Excess: As a water-soluble vitamin, any surplus vitamin C that isn't absorbed or used by the body is filtered by the kidneys and excreted in the urine, mostly within 24 hours.
Oral vs. IV Routes: Oral intake is tightly regulated, preventing excessively high blood levels. Intravenous (IV) administration bypasses this control, resulting in much higher blood concentrations that are also cleared quickly by the kidneys.
Influencing Factors: Smoking, body weight, illness, and genetics all impact vitamin C metabolism. Smokers and heavier individuals, for example, have higher vitamin C requirements due to increased oxidative stress and volumetric dilution.
The Kidney's Role: The kidneys actively reabsorb vitamin C to maintain optimal body levels, but this process becomes saturated when intake is very high, leading to increased urinary excretion.
Optimal Strategy: To maintain a steady supply, it is most effective to consume vitamin C regularly from food or split supplement doses, rather than relying on large, infrequent mega-doses.

The Journey of Vitamin C: From Intake to Elimination

Vitamin C, or ascorbic acid, is a water-soluble vitamin essential for many bodily functions, including immune health, collagen synthesis, and wound healing. Unlike fat-soluble vitamins, which can be stored in the body's fatty tissues, vitamin C cannot be stockpiled for long periods. This means a continuous supply from your diet is necessary to maintain adequate levels. The speed at which vitamin C moves through your body is not uniform; it's a multi-stage process involving absorption, distribution to tissues, and eventual excretion.

The Two-Phase Process of Absorption and Clearance

For most people, the typical absorption of vitamin C from food ranges from 70% to 90% for moderate intakes of 30 to 180 milligrams (mg) per day. This absorption primarily occurs in the small intestine via a dose-dependent, sodium-dependent active transport mechanism. The efficiency of this process, however, decreases significantly as the intake dose increases. For doses over 1 gram (1,000 mg) per day, the absorption rate can drop to less than 50%. Any unabsorbed vitamin C from high doses is typically excreted in the feces or metabolized by intestinal flora.

Once absorbed, vitamin C enters the bloodstream, but its concentration is tightly regulated by the kidneys. At normal physiological levels, the kidneys reabsorb almost all the filtered vitamin C, preventing its loss. However, once plasma concentrations rise above a certain threshold (around 45-60 μmol/L), the renal reabsorption transporters become saturated, and any excess is excreted in the urine.

Dual Half-Lives: Plasma vs. Whole-Body

To fully understand how long vitamin C stays in the body, it's crucial to distinguish between its plasma half-life and its whole-body half-life. They describe two different speeds of turnover.

Plasma Half-Life: This refers to how quickly the vitamin C concentration in the bloodstream decreases by half. After a single oral dose, the plasma half-life is quite short, often reported to be between 30 minutes and 2 hours. This explains why a large dose causes a rapid, but temporary, spike in blood levels before returning to baseline as the kidneys excrete the excess.
Whole-Body Half-Life: This measures the depletion rate of the body's entire vitamin C store, including the vitamin C stored in tissues like the adrenal glands, brain, and pituitary gland. Because the body carefully conserves its tissue stores, the whole-body half-life is much longer, ranging from 10 to 20 days. This slower turnover is why consistent, daily intake is recommended rather than relying on intermittent high doses.

Factors Influencing Vitamin C's Journey Through the Body

Several physiological and lifestyle factors can significantly impact how quickly vitamin C is metabolized and excreted:

Smoking: Smokers have much lower vitamin C status than non-smokers and require a higher intake to maintain adequate levels. This is because smoking increases oxidative stress, which depletes the body's vitamin C reserves more rapidly.
Body Weight: Individuals with a higher body weight, particularly those with obesity, often require more vitamin C to reach the same circulating concentrations as lighter individuals. This is partly due to volumetric dilution, where the same dose is distributed across a larger body volume.
Illness and Stress: During periods of illness, infection, or severe stress, the body's demand for vitamin C increases dramatically. Inflammatory processes and enhanced oxidative stress consume the vitamin at a faster rate, leading to lower plasma concentrations. This is why intake requirements go up during illness.
Genetics: Variations in the genes that encode vitamin C transporters (like SVCT1) can influence intestinal absorption and renal reabsorption rates. This means some people may have a natural tendency to excrete more vitamin C than others.
Age: Older adults may have an attenuated serum response to vitamin C intake at lower doses, though this can be influenced by other health and lifestyle factors common in this population.

Oral vs. Intravenous Administration

The route of administration plays a critical role in how quickly vitamin C goes through your body. There are key differences in pharmacokinetics between oral and intravenous (IV) delivery that affect plasma concentration and clearance.


Feature	Oral Administration	Intravenous (IV) Administration
Peak Plasma Levels	Tightly controlled, limited peak concentrations (~220 μmol/L predicted at max tolerated dose).	Bypasses oral absorption control, leading to much higher plasma levels (up to 70x higher).
Absorption Control	Regulated by specific transporters in the gut, which become saturated at high doses.	Bypasses the gastrointestinal tract, enabling direct entry into the bloodstream.
Excretion Rate	Excess is excreted via urine, typically within 24 hours, at high intake levels.	Cleared from the bloodstream relatively quickly, often within a few hours for the initial high concentration, with quantitative renal clearance observed within 24 hours.
Purpose	Daily supplementation or obtaining from food for general health.	Used in therapeutic settings (e.g., specific cancer treatments) to achieve pharmacological concentrations.

Optimizing Your Vitamin C Intake

To maximize the benefits of your vitamin C intake, consider these strategies:

Prioritize Food Sources: The most bioavailable and consistent source of vitamin C is a diet rich in fruits and vegetables. Since absorption is most efficient at moderate doses, eating vitamin C-rich foods daily is the best approach.
Space Out Supplements: If you use supplements, avoid taking very high doses all at once. Spreading out smaller doses throughout the day can improve overall absorption and maintain more consistent blood levels.
Adjust for Lifestyle: If you are a smoker, have a higher body weight, or are experiencing illness, your body's vitamin C turnover rate will be faster. In these situations, your requirements are higher and you may need to increase your intake to compensate for the accelerated depletion.
Consider Dosage: For a healthy adult, daily intake to reach adequate plasma concentrations is around 75-110 mg/day. Taking supplements providing 200-400 mg can saturate tissues, but doses exceeding 1 gram offer diminishing returns on absorption.

Conclusion

The speed at which vitamin C moves through your body is highly dynamic and depends on multiple factors. While excess vitamin C from a single dose is quickly flushed out of the bloodstream within a few hours, the body’s total reserve within tissues has a much longer half-life of 10–20 days. Absorption efficiency decreases with higher oral doses, making consistent, moderate intake from food or spaced-out supplements the most effective way to maintain healthy levels. Conditions like smoking, obesity, and illness increase the speed of vitamin C metabolism, necessitating higher intake to meet the body's demands.

For more detailed information on vitamin C requirements, refer to the NIH Office of Dietary Supplements Vitamin C Fact Sheet.

Frequently Asked Questions

No, quite the opposite. Your body’s ability to absorb vitamin C decreases as the dosage increases. For high doses, a large portion is not absorbed and the excess that does enter the bloodstream is filtered by the kidneys and quickly excreted in the urine, often within hours.

Plasma half-life is how fast vitamin C levels drop in your blood (typically 30 minutes to 2 hours after a single dose). Whole-body half-life refers to the slower depletion of your body’s total stored vitamin C reserves in tissues, which can take 10 to 20 days.

Smokers require more vitamin C because the oxidative stress caused by smoking depletes their body's vitamin C reserves much faster than in non-smokers. Studies have shown they need a significantly higher daily intake to maintain adequate levels.

Excess vitamin C is metabolized into oxalate, which is excreted in the urine. For most healthy individuals, this is not a concern. However, in predisposed individuals, especially men taking high supplemental doses (over 1000 mg/day), the increased urinary oxalate can potentially contribute to kidney stone formation.

To maximize absorption, prioritize moderate daily intake from food sources. If using supplements, take them in smaller, spaced-out doses (e.g., 200-400 mg at a time) to avoid saturating your intestinal transporters and to maintain more stable blood levels.

Yes, a major difference exists. Oral intake is tightly regulated by gut absorption, preventing excessively high blood concentrations. IV administration bypasses this control, leading to much higher plasma levels. Both are ultimately excreted by the kidneys within 24 hours, but the peaks are vastly different.

The vitamin C that isn't absorbed by the small intestine and enters the large intestine can be metabolized by intestinal flora or excreted in the feces. The absorbed but unused portion in the bloodstream is filtered and excreted through the urine.