Is Vitamin B12 Affected by Light and How to Protect It?

October 7, 2025 •

4 min read

Yes, vitamin B12 is notably sensitive to light, especially ultraviolet (UV) light, which causes a process called photodegradation. This chemical reaction can significantly reduce the vitamin's potency and effectiveness over time if not stored properly.

Quick Summary

Vitamin B12 is sensitive to light, heat, and moisture, which can trigger photodegradation and reduce its efficacy. Proper storage is essential to maintain the supplement's potency and ensure optimal health benefits. Different forms of the vitamin, like cyanocobalamin and methylcobalamin, exhibit varying degrees of light sensitivity in aqueous solutions. Protective packaging and storage in cool, dark places are key methods to minimize degradation.

Key Points

Significant Light Sensitivity: Vitamin B12 is highly sensitive to light, especially ultraviolet (UV) and blue wavelengths, which can trigger a chemical breakdown known as photodegradation.
Reduced Potency Over Time: Exposure to light causes the vitamin's structure to degrade, leading to a loss of biological activity and reduced effectiveness of supplements.
Proper Storage is Crucial: Store vitamin B12 supplements in opaque, airtight containers and keep them in a cool, dark place away from direct sunlight and heat to preserve their potency.
Formulations Vary in Stability: Different forms of B12 have different levels of light sensitivity. Cyanocobalamin is more stable than methylcobalamin in solution, which is particularly photolabile.
Food Sources Need Protection Too: While packaged for protection, food sources and liquids containing B12 should also be shielded from light to minimize degradation.
Observe Packaging for Guidance: Pharmaceutical and supplement manufacturers recommend storing B12 products protected from light, a guideline that should be followed closely.

The Chemical Nature of Vitamin B12's Light Sensitivity

Vitamin B12, or cobalamin, is a complex, cobalt-containing compound that is highly susceptible to degradation when exposed to light. The core of its molecule, the corrin ring, along with the cobalt-carbon bond, is vulnerable to photochemical reactions. This process, known as photolysis, breaks down the molecule into less effective or inactive fragments. The rate and extent of this degradation depend on several factors, including the type of light, exposure duration, and the specific chemical form of the vitamin.

How Different Light Sources Impact B12

Not all light is created equal when it comes to affecting vitamin B12. Research has shown that shorter-wavelength light, such as ultraviolet (UV) and blue light, causes more significant damage than longer wavelengths, like red light.

Ultraviolet (UV) Light: Both UV-A and UV-B radiation are highly damaging, leading to rapid and substantial degradation of B12. This is a major reason why B12 supplements are often sold in opaque or colored bottles to block UV rays.
Visible Light: While less destructive than UV, visible light—especially the blue spectrum—can still cause B12 to break down over time, particularly in liquid solutions. Controlled experiments have shown that even regular lab fluorescent light can cause measurable degradation within minutes.
Monochromatic Light: Studies using specific color filters have confirmed that photolysis is more pronounced in the short-wavelength regions of the spectrum. This further solidifies the need for protection from broad-spectrum light sources, including direct sunlight.

Comparison of B12 Forms and Their Photostability

Different chemical forms of vitamin B12 have varying levels of stability, which affects their storage and handling requirements. Cyanocobalamin is generally the most stable form, while methylcobalamin and adenosylcobalamin are more sensitive to light.


Feature	Cyanocobalamin	Methylcobalamin	Hydroxocobalamin
Photostability	Higher stability	Very unstable/photolabile	Moderately unstable
Mechanism	Light replaces the cyanide ligand with a hydroxyl group, forming hydroxocobalamin.	Undergoes photoreduction to form hydroxocobalamin.	Susceptible to irreversible oxidative degradation.
Storage Guidance	Store in airtight, light-resistant containers.	Protect from light; some formulations require refrigeration.	Protect from light; store in cool, dark place.
Common Use	Most common and stable form for supplementation.	Used for specific neurological conditions; growing use in supplements.	Less common, often used in injections.

Practical Tips for Protecting Vitamin B12 from Light

To ensure your vitamin B12 remains potent, it is crucial to protect it from light exposure, whether in supplement form or from food sources.

Storing Vitamin B12 Supplements

Most high-quality B12 supplements come in protective packaging for a reason. Here are key practices for proper storage:

Keep in original container: The opaque or amber-colored bottle is designed specifically to block light and moisture. Do not transfer tablets or capsules to a clear container.
Store in a cool, dark place: High temperatures and light accelerate degradation. A kitchen cabinet away from the stove or a pantry shelf is ideal, not a bathroom medicine cabinet with high humidity.
Mind liquid and injectable forms: Vitamin B12 in aqueous solution is particularly vulnerable to light. Vials and nasal sprays should be kept in their carton until use and protected from light.

Handling and Using B12 Supplements

Minimize exposure during use: When taking a tablet, quickly remove one from the bottle and close it. Do not leave the lid off for extended periods, especially in bright rooms.
Be aware of combination supplements: If your B12 is part of a B-complex vitamin, understand that interactions with other vitamins (like B1 and C) can also affect its stability.

Protecting B12 from Food Sources

While light's impact on fortified foods is generally minimal due to packaging, it's wise to be mindful of natural food sources, though degradation is less of a concern than with concentrated supplements.

Limit dairy exposure: Milk, a source of B12, is sold in opaque or cardboard containers to protect light-sensitive vitamins, including B12 and riboflavin (B2).
Cook and store properly: Heat and prolonged cooking can also cause vitamin loss. Minimize cooking times and store leftover foods containing B12 (like meat, fish, and eggs) in sealed, opaque containers in the refrigerator.

Conclusion: Prioritize Proper Storage for B12 Potency

The scientific evidence is clear: is vitamin B12 affected by light? The answer is a resounding yes. Exposure to light, particularly UV and blue wavelengths, can trigger photodegradation, reducing the vitamin's potency and effectiveness. This is especially true for methylcobalamin in aqueous solutions, which is more photolabile than the more stable cyanocobalamin. For consumers, this highlights the critical importance of storing supplements correctly—in opaque, airtight containers, away from direct sunlight, heat, and moisture. By taking these simple precautions, you can ensure that you are receiving the full health benefits from your B12 intake and avoid the pitfalls of degraded supplements.

Vitamin B12 in Foods, Food Supplements, and Medicines—A Review of its Stability

Frequently Asked Questions

Yes, light can destroy vitamin B12 through a chemical process called photolysis, which breaks down the vitamin's molecular structure and reduces its potency, especially in liquid solutions.

You should store vitamin B12 supplements in a cool, dark place inside their original, opaque container to protect them from both light and moisture.

Both natural sunlight and artificial light can be damaging. Natural sunlight, particularly its UV component, is highly destructive. However, strong artificial light, like fluorescent bulbs, can also cause measurable degradation, especially over time.

No, different forms have varying sensitivities. Cyanocobalamin is the most stable, while methylcobalamin and adenosylcobalamin are more sensitive and prone to photodegradation.

Light can affect B12 in food sources, but it is a more significant concern for concentrated supplements. Many food products containing B12, like milk, are packaged to protect against light.

Yes, B12 injections and nasal sprays, which are typically in liquid form, are very sensitive to light. They should be stored in their original packaging, protected from light, and in a cool place.

No, standard B12 tablets do not typically need to be refrigerated. However, some liquid or injectable formulations may require refrigeration for optimal stability, and all forms must be kept away from excessive heat and light.