Which vitamin gets excreted in urine?

October 19, 2025 •

2 min read

Over 89% of vitamin C is typically excreted through urine when dietary intake exceeds what the body can use. This rapid elimination is a key characteristic of water-soluble vitamins and directly answers the question: which vitamin gets excreted in urine.

Quick Summary

Excess water-soluble vitamins, including C and most B vitamins, are not stored significantly and are flushed from the body via urine, requiring consistent daily replenishment.

Key Points

Water-Soluble Vitamins: Excess amounts of vitamin C and most B-complex vitamins are excreted in urine because the body has limited storage capacity for them.
Fat-Soluble Vitamins: Vitamins A, D, E, and K are not excreted via the urine but are instead stored in the body's liver and fatty tissues.
Daily Intake: Regular consumption of water-soluble vitamins is necessary to prevent deficiency, as the body cannot maintain long-term reserves.
B12 Exception: Vitamin B12 is a water-soluble vitamin but can be stored in the liver for several years, making it an exception to the rule of rapid excretion.
Toxicity Risk: Water-soluble vitamins have a lower risk of toxicity than fat-soluble vitamins because excess amounts are readily flushed out.
Kidney's Role: The kidneys play a vital role in filtering the blood and excreting excess water-soluble vitamins to maintain the body's nutritional balance.
High-Dose Effects: While rare, ingesting megadoses of certain water-soluble vitamins, such as C or B6, can still lead to adverse side effects.

Water-Soluble vs. Fat-Soluble: Understanding the Difference

Vitamins are essential nutrients categorized into two groups based on solubility: water-soluble and fat-soluble. Water-soluble vitamins dissolve in water, are easily absorbed, and not stored in large amounts. Excess is filtered by the kidneys and excreted in urine. Fat-soluble vitamins require dietary fat for absorption, are stored in the liver and fatty tissues, and can accumulate, increasing toxicity risk in excess.

The Swift Exit: Water-Soluble Vitamins

The water-soluble group includes all B-complex vitamins and vitamin C. Because they aren't stored significantly (except B12), regular intake is needed. The eight B vitamins have diverse metabolic roles. Vitamin B2 (Riboflavin) can cause urine to appear bright yellow when in excess. Vitamin B12 is unique among water-soluble vitamins as it can be stored in the liver for years. Vitamin C is an antioxidant important for tissue repair and immunity, with excess also excreted by the kidneys.

The Long-Term Storage: Fat-Soluble Vitamins

Fat-soluble vitamins (A, D, E, K) are stored in the body and not excreted in urine. Their ability to accumulate means high doses, particularly from supplements, can lead to toxicity.

Water-Soluble vs. Fat-Soluble Vitamins: A Comparison


Feature	Water-Soluble Vitamins (B-complex, C)	Fat-Soluble Vitamins (A, D, E, K)
Absorption	Directly absorbed into the bloodstream	Absorbed with dietary fats into the lymphatic system
Storage	Limited storage capacity; must be replenished regularly (except B12)	Stored in the liver and fatty tissues
Excretion	Excess is flushed out through the kidneys into urine	Not excreted via urine; accumulated in the body
Toxicity Risk	Generally low, as excess is excreted	Higher, as excess can accumulate to toxic levels

The Role of the Kidneys in Excretion

The kidneys filter blood and excrete waste. For water-soluble vitamins, the kidneys filter out excess amounts, which are then passed into the urine, maintaining nutrient balance. Kidneys regulate carriers for fat-soluble vitamins but don't excrete them directly in the same way.

Is Excess Always Harmless?

While toxicity from water-soluble vitamins is rare due to excretion, very high supplement doses can cause issues. Excessive vitamin C can cause digestive problems and potentially increase kidney stone risk. High doses of Niacin (B3) can lead to flushing or liver damage, and prolonged megadoses of B6 can cause nerve damage. These issues are primarily linked to supplements, not food intake. A balanced diet is the best way to get vitamins.

Conclusion: The Importance of Balance

Water-soluble vitamins, including vitamin C and most B-complex vitamins, are excreted in urine because they aren't stored effectively. This natural safety mechanism means consistent daily intake from a healthy diet is important. Fat-soluble vitamins are stored, leading to different considerations for intake and potential toxicity. Understanding how your body handles these vitamins helps you make informed health choices. For more information, consult the MedlinePlus Medical Encyclopedia.

Frequently Asked Questions

The water-soluble vitamins include vitamin C and all eight B-complex vitamins: B1 (Thiamine), B2 (Riboflavin), B3 (Niacin), B5 (Pantothenic Acid), B6 (Pyridoxine), B7 (Biotin), B9 (Folate), and B12 (Cobalamin).

While the body's ability to excrete excess amounts reduces the risk of toxicity, overdosing is possible with very high doses, typically from supplements. Excessive intake of vitamins like B6 and niacin can cause adverse side effects.

Excessive vitamin C intake can lead to gastrointestinal issues like diarrhea and nausea. Chronic high doses can also increase the risk of kidney stones in some individuals.

No, fat-soluble vitamins (A, D, E, and K) are not excreted through the urine. They are stored in the body's fatty tissues and liver for long periods.

This is often caused by the excretion of excess Riboflavin (vitamin B2), which has a naturally bright yellow fluorescence. This is harmless and indicates your body is eliminating what it doesn't need.

While it is a water-soluble vitamin, B12 is an exception. The body has a unique mechanism to store it in the liver for several years, so excess amounts are not immediately excreted like other B vitamins.

Excess water-soluble vitamins are typically flushed out of the body within a few hours to a day after consumption, which is why a regular supply is needed.