Am I Absorbing My Vitamins

Bright yellow urine after taking a multivitamin is usually harmless, but it may be a sign you are taking more B vitamins than your body needs.

Dietitian Andrea du Plessis explains why this happens, how to tell if you’re absorbing your supplements, and how to optimise nutrient uptake while avoiding waste.

Question:
I have been taking a multivitamin, but after a couple of hours my urine turns a neon yellow colour. Does this mean I’m not taking them with enough water, or that my body isn’t absorbing the vitamins, in other words, am I throwing good money down the toilet?
Jane

ANDREA DU PLESSIS REPLIES:

Urine colour can vary widely depending on hydration, diet, and supplement use. The normal pale yellow colour is due to waste products and the breakdown of nutrients in the body.

Hydration factor:
The most common reason for darker yellow urine is dehydration, which can be easily corrected by increasing water intake.

Dietary factors:
Some foods, like beetroot, can cause harmless colour changes, in this case, a pinkish or purple hue, due to the breakdown of natural pigments.

Vitamin factor:
Bright, almost fluorescent yellow urine is most often linked to B vitamin supplements, especially riboflavin (vitamin B₂). This colour change is harmless and reflects:

  1. The breakdown products of B vitamins in the body.

  2. Excretion of B vitamins that were absorbed but not stored or used immediately.

Because B vitamins are water-soluble, your body does not store them in large quantities. Once your immediate needs are met, any excess is eliminated via urine. This does not necessarily mean your body isn’t absorbing them, but it may indicate you are taking more than you need, which can be financially wasteful over time.

How to optimise your B vitamin absorption:

  • Take your multivitamin with breakfast, ideally a meal containing protein and healthy fats, to slow digestion and improve nutrient uptake.

  • Check whether other supplements or fortified foods you consume also contain B vitamins. You may be doubling up unnecessarily.

  • Consider reducing your intake frequency (e.g. every second day) if your diet is already nutrient-rich and the bright colour persists.

  • Pair with a balanced diet that includes whole food sources of B vitamins (leafy greens, eggs, fish, legumes), reducing reliance on high-dose supplements.

The goal is not to avoid yellow urine entirely, but to ensure you are giving your body what it needs without unnecessary excess.

Editor's note: Here is an article Andrea wrote about The Vitamin C Breakdown – Sensible Supplementation. 

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