What vitamin causes urine to turn neon yellow? The role of riboflavin explained

January 6, 2026 •

2 min read

The color of your urine is a powerful, yet often overlooked, health indicator. Many people are surprised to find their urine has taken on a fluorescent, almost neon yellow hue after starting a new supplement regimen. It's a very common side effect, but what vitamin causes urine to turn neon yellow? The answer primarily lies with riboflavin, also known as vitamin B2.

Quick Summary

Excess riboflavin (vitamin B2) consumed from supplements or multivitamins is the most common cause of neon yellow urine. As a water-soluble vitamin, the body excretes the surplus, and the B2's natural pigment gives urine its bright color. This is a harmless side effect of eliminating unneeded nutrients.

Key Points

Riboflavin (Vitamin B2): This water-soluble vitamin is the primary reason for neon yellow urine, particularly after taking supplements or multivitamins.
Harmless Side Effect: The vivid color is a normal and temporary sign of the body processing and excreting excess riboflavin, and is not a cause for concern.
Supplements vs. Food: Higher doses of riboflavin are often found in supplements, which more frequently cause the color change than riboflavin from food sources.
Other B Vitamins: Other water-soluble B vitamins, such as folic acid (B9) and B12, can also contribute to urine discoloration.
Excretion Process: The color comes from riboflavin's natural yellow-green pigment, which becomes visible as it is flushed out by the kidneys.
Not a Sign of Poor Absorption: Neon yellow urine does not mean you are not absorbing your vitamins; it simply means your body is clearing what it doesn't need at that moment.

The Primary Culprit: Riboflavin (Vitamin B2)

If you've recently started a supplement containing B vitamins and noticed your urine has changed to a vivid yellow, the most likely cause is riboflavin, or vitamin B2. This effect, often called "luminous wee," occurs because riboflavin has a natural yellow-green, fluorescent pigment. When you ingest more than your body can use, the excess is simply excreted through your kidneys, causing the dramatic color change.

How Your Body Handles Riboflavin

Riboflavin, like all B-complex vitamins and vitamin C, is water-soluble. This means your body cannot store it in large quantities. Instead, it uses what it needs for essential functions and passes any surplus into the urine. This process of clearing excess vitamins is harmless and temporary.

Functions of riboflavin include energy production and supporting healthy skin, eyes, and nerve function. It also acts as an antioxidant.

Understanding B-Complex Supplements

Many multivitamins and B-complex supplements contain higher doses of riboflavin than recommended daily allowances. Manufacturers often include higher amounts as a safety measure since the excess is eliminated and high doses are considered generally safe.

Other Potential Causes of Urine Color Changes

While riboflavin is the main reason for neon yellow urine, other factors can also change urine color, including dehydration and other supplements.

Comparison Table: Causes of Urine Color Changes


Cause	Typical Urine Color	Explanation
Excess Riboflavin	Neon or fluorescent yellow	Your body excretes surplus, water-soluble B2 via urine. Harmless.
Dehydration	Dark yellow or amber	Concentrated urine due to a low fluid intake. Requires drinking more water.
Vitamin C	Bright yellow or orange	High doses, especially from supplements, can be excreted and change color. Harmless.
Beta-carotene	Deep yellow or orange	Excess intake from foods like carrots or sweet potatoes. Harmless.
Medications	Various (blue, green, orange)	Some drugs like phenazopyridine (for urinary tract pain) or certain antibiotics can alter urine color. May be temporary.
Medical Conditions	Red, brown, cloudy	Can signal more serious issues like liver problems, kidney disease, or urinary tract infections. Requires medical attention.

Foods Rich in Riboflavin

While supplements are a common source of excess riboflavin, you can also obtain this vitamin through your diet. Foods such as dairy products, fortified cereals and breads, lean meats, eggs, leafy greens, nuts, and legumes contain riboflavin.

What to Do About Neon Yellow Urine

Seeing neon yellow urine after taking vitamins is generally a sign your body is processing the nutrients effectively. If the color is bothersome, you can consider reducing your supplement dosage or splitting your dose throughout the day. Staying well-hydrated is also important for overall urine health, though it won't prevent the color change caused by riboflavin.

Conclusion: A Harmless and Healthy Sign

In summary, neon yellow urine is usually caused by excess riboflavin (vitamin B2) from supplements. It's a harmless, normal process where the kidneys filter out the surplus water-soluble vitamin. While startling, it indicates proper bodily regulation. However, consult a healthcare provider for unusual odor, pain during urination, or red/brown color.

Frequently Asked Questions

No, neon yellow urine caused by vitamin supplements is not dangerous. It is a completely harmless and normal physiological process of your body eliminating excess water-soluble vitamins, primarily riboflavin (B2).

No, this is a common misconception. Your body absorbs what it needs, and the excess is simply excreted. The bright color is a sign of this natural, efficient process, not an indicator of poor absorption.

Severe dehydration is another common cause of dark or bright yellow urine because the pigments become more concentrated. Certain medications and foods with strong dyes or pigments can also alter urine color.

No, you do not need to stop. The color change is a harmless side effect. However, if you are concerned, you could try a lower-dose supplement or split your daily intake into smaller, more frequent doses.

While all B vitamins are water-soluble, riboflavin (B2) is the most prominent cause of neon yellow urine due to its distinct, fluorescent yellow-green pigment. Folic acid and B12 can also contribute to color changes, especially in combination.

The neon yellow color is temporary and will fade as your body processes and excretes the excess vitamins. It typically returns to a normal pale yellow within a few hours to a day after taking the supplement.

The recommended daily allowance (RDA) for riboflavin is 1.3 mg for adult men and 1.1 mg for adult women. Most supplements contain much higher amounts, which is why color changes are so common.