Does vitamin B12 have to be protected from light?

November 28, 2025 •

3 min read

According to scientific research, aqueous solutions of cyanocobalamin, a common form of B12, are known to be sensitive to light. The answer to whether vitamin B12 has to be protected from light is a definitive yes, as exposure can significantly degrade its potency and stability. This is especially critical for liquid formulations and injectable forms of the vitamin, where photodegradation occurs more rapidly.

Quick Summary

Vitamin B12 is highly sensitive to light, which can trigger photolysis and degrade its potency, particularly in liquid forms. Proper storage away from direct and indirect light is essential for maintaining the vitamin's effectiveness. Factors like formulation, light intensity, and duration of exposure all influence the rate of degradation.

Key Points

Yes, it must be protected: Vitamin B12 is highly sensitive to light, which can degrade its potency over time.
Liquid forms are most vulnerable: The degradation process, called photolysis, is significantly faster in liquid vitamin B12 (e.g., injections, drops) than in solid tablets.
UV light is the primary threat: Studies show that ultraviolet (UV) light, found in direct and indirect sunlight, is especially damaging to the cobalamin molecule.
Store in a cool, dark place: Proper storage in an opaque container away from heat, moisture, and light is the best way to preserve the vitamin's effectiveness.
Injections require extra care: Injectable B12 vials should be kept in amber glass or wrapped in aluminum foil to block out light completely.
Look for opaque packaging: Manufacturers often use dark-colored glass bottles for B12 supplements to protect them from light exposure during storage.
Discard if expired or discolored: A loss of potency over time is normal, but visible changes like a color shift can indicate significant degradation.
Other vitamins can accelerate breakdown: In liquid solutions, vitamins like B2 and C can act as photosensitizers, speeding up B12's photodegradation.

Why Is Vitamin B12 Sensitive to Light?

Vitamin B12, particularly its active forms (cobalamins), is susceptible to degradation from light, a process called photolysis. This occurs because the molecule contains a reactive organometallic bond that can be broken by light energy, especially UV radiation. This breakdown leads to less active compounds. Liquid B12 forms, like injections and oral drops, are more prone to rapid photolysis.

The Science Behind Photolysis

Photolysis is driven by light energy breaking the bond within the B12 molecule's core cobalt atom. While UV light is most detrimental, intense visible light also contributes to degradation. Certain conditions, such as specific pH ranges in liquids and the presence of other vitamins like B2 and C, can accelerate this process.

Proper Storage to Protect Your Supplements

Storing vitamin B12 properly is key to maintaining its effectiveness. Always keep supplements in a cool, dark, and dry place.

Supplements in Opaque Containers: Many manufacturers use dark or tinted glass bottles to protect B12 from light. Keep supplements in their original packaging.
Keep Out of Sunlight: Avoid storing B12 in sunlit areas, including windowsills. High temperature and humidity areas like kitchens and bathrooms are also not ideal.
Injectable Vitamin B12: Injectable B12 often comes in amber vials. Additional protection, such as wrapping vials in aluminum foil after opening or mixing, is often recommended to minimize light exposure.

Comparison of B12 Formulation Stability


Feature	Liquid B12 (Oral Drops/Injections)	Solid B12 (Tablets/Capsules)
Light Sensitivity	High, especially after the original vial is opened and exposed. Photolysis is a rapid process in aqueous solution.	Significantly lower. The dry form is much more stable against light degradation.
Onset of Degradation	Can begin within minutes of exposure to intense light.	Degradation is a much slower, gradual process over time, even with poor storage.
Storage Method	Requires strict protection from light and heat. For injections, protect from light even during the preparation process.	Store in its original, opaque container in a cool, dark, and dry location.
Other Vulnerabilities	More sensitive to changes in pH and the presence of other vitamins like B2 and C, which can accelerate degradation.	Less vulnerable to chemical interactions and environmental changes compared to liquid forms.
Best Practice for Users	Administer quickly after drawing into a syringe. Cover the vial in foil for long-term storage after opening.	Always keep the lid tightly sealed and store in a stable, dark environment.

Other Environmental Factors Affecting B12

Besides light, vitamin B12 stability is affected by other environmental factors:

Heat and Moisture: High temperatures and humidity can speed up B12 degradation. Storage in humid areas like bathrooms should be avoided, and temperatures above 30°C (86°F) are not recommended.
pH Levels: In liquid formulations, the pH significantly impacts stability, with optimal stability typically found between pH 4.0 and 6.5.
Interactions with Other Vitamins: Certain vitamins, including riboflavin (B2) and ascorbic acid (vitamin C), can make B12 more susceptible to light-induced breakdown when they are together in a liquid solution.

Conclusion

It is essential to protect vitamin B12 from light to maintain its potency. Light, particularly UV, triggers photolysis, degrading the active cobalamin molecules. Liquid and injectable B12 are most vulnerable, but all forms should be stored in a cool, dark, and dry location. Following proper storage guidelines ensures your supplements remain effective.

Practical Steps for Storage

Keep supplements in their original, opaque containers.
Store bottles in a dark cupboard or drawer away from light.
Avoid storing B12 in kitchens or bathrooms due to temperature and humidity fluctuations.
For injectables, consider wrapping vials in aluminum foil for added light protection.
Check expiration dates and discard expired supplements, as potency decreases over time.

Frequently Asked Questions

In liquid solutions, vitamin B12 degradation from light can occur quite rapidly. For example, exposure to direct sunlight has been shown to cause a 10% loss of potency within just 30 minutes.

While it is generally not harmful to take expired vitamin B12, the supplement will have lost a significant amount of its potency and may not be effective. It is best to use supplements before their expiration date.

Yes, light can degrade vitamin B12 in food, though the effects are less pronounced than in concentrated liquid supplements. The packaging and processing of fortified foods are designed to minimize light exposure to preserve nutrients.

Injectable B12 vials are often wrapped in aluminum foil to provide complete protection from light. This is especially important for multi-dose vials that will be exposed to light repeatedly when opened.

Yes, even fluorescent light contains wavelengths that can cause photodegradation of vitamin B12, particularly over prolonged exposure. Storing supplements in a dark cabinet prevents this issue.

When B12 is degraded by light, the active cobalamin molecule undergoes a chemical change, breaking the cobalt-carbon bond. This results in the formation of other cobalamin forms, such as hydroxocobalamin, which may not be as potent or readily used by the body.

Yes, refrigerated B12 still requires protection from light. While the cool temperature helps with overall stability, it does not prevent the light-induced degradation process known as photolysis. Store refrigerated liquid B12 in an opaque, light-blocking container.

A vitamin B12 supplement in a clear glass bottle is more susceptible to light-induced degradation and may be less potent over its shelf life compared to a supplement stored in an opaque, amber bottle. If you have such a bottle, keep it in a dark place.

While convenient, a clear plastic pill organizer offers no protection from light. It is best to fill your pill organizer weekly and store the bulk of your supplements in their original, light-protective container in a dark, cool place to prevent potency loss.