Can B12 Go Bad? Understanding Shelf Life and Potency

January 8, 2026 •

4 min read

Most vitamins, including B12, have an average shelf life of about two years from the date of manufacture, according to industry standards. While the supplements won't spoil like food, this longevity can be cut short if not stored properly, which leads many to wonder, "can B12 go bad?" The answer lies not in spoilage, but in a gradual loss of potency over time, which can render the supplement less effective for those who depend on it for nutrient needs.

Quick Summary

Vitamin B12 supplements lose their potency over time due to factors like heat, light, and moisture. The labeled expiration date indicates when the manufacturer guarantees full strength. Expired B12 is typically not toxic but may not provide the intended health benefits, which is especially important for those with a deficiency.

Key Points

Loss of Potency: Expired B12 isn't toxic, but it gradually loses its strength and effectiveness over time.
Environmental Factors: Heat, light, oxygen, and moisture accelerate the chemical degradation of vitamin B12.
Storage Matters: Proper storage in a cool, dark, and dry place is crucial for maximizing a supplement's shelf life.
Check for Spoilage: Visible mold, strange odors, or changes in color/texture are signs that a supplement is compromised and should be discarded.
Manufacturer Guarantee: The expiration date is the point up to which the manufacturer guarantees the full potency of the product.
Risk for Deficient Individuals: For those with a B12 deficiency, relying on an expired, weakened supplement could undermine treatment.
Solid vs. Liquid Forms: Tablets and capsules are generally more stable than liquid or gummy forms, which are more sensitive to moisture and light.

The Science Behind Vitamin Degradation

Unlike perishable food items that grow mold and bacteria, vitamin supplements degrade chemically, losing their effectiveness rather than becoming dangerous. For water-soluble vitamins like B12 (cobalamin), this process is influenced by several environmental factors. The chemical structure of B12, with its central cobalt atom and corrin ring, makes it susceptible to degradation via various pathways.

Key Factors That Compromise B12 Potency

Light Exposure: Vitamin B12 is highly sensitive to light, a process known as photodegradation. Exposure to direct sunlight or even prolonged fluorescent light can significantly reduce its potency over time. This is why B12 supplements are often sold in opaque, dark-colored bottles.
Heat and Temperature Fluctuations: High temperatures accelerate the degradation of vitamin compounds. Storing supplements in a hot car, a kitchen cabinet near the stove, or a steamy bathroom can cause the active ingredients to break down faster. Consistent, cool storage is crucial for maintaining potency.
Moisture and Humidity: Water-soluble vitamins like B12 are particularly vulnerable to moisture. Humid environments, such as a bathroom medicine cabinet, can introduce moisture into the container, causing tablets and powders to degrade more quickly. This can lead to discoloration, clumping, or the development of mold.
Oxygen Exposure: Once a supplement bottle is opened, the vitamin is exposed to oxygen, which can cause oxidation and reduce its strength. Keeping the lid tightly sealed and storing supplements in airtight containers helps minimize this effect.

Comparing Different B12 Supplement Forms

Not all B12 supplements are created equal when it comes to stability. The form of the vitamin (e.g., tablet, liquid, gummy) and its chemical variant (e.g., cyanocobalamin, methylcobalamin) can affect its shelf life.


Feature	Tablets/Capsules	Liquid/Gummies
Moisture Sensitivity	Generally low. Desiccant packets are often included to absorb excess moisture.	High. Liquid and gummy formulas are more susceptible to moisture and humidity.
Potency Loss Rate	Slower, as the solid form provides more stability for the active ingredient.	Faster, due to higher exposure to moisture and other ingredients.
Light Sensitivity	Protects the active ingredient somewhat, especially in opaque packaging.	More vulnerable to photodegradation; often stored in dark glass or opaque plastic bottles.
Storage Conditions	Requires a cool, dry place away from heat and light.	May require refrigeration after opening to maintain stability and effectiveness.

What the Expiration Date Means

The expiration or 'best by' date on a B12 supplement is the manufacturer's guarantee that the product will contain 100% of the listed nutrient dosage up to that date, provided it is stored properly. After this date, the supplement won't suddenly become toxic, but its potency will begin to progressively decline. For individuals relying on the supplement to correct a vitamin deficiency, this gradual loss of potency means they may not be receiving the full dose and could risk their health goals. For those without a deficiency, an expired supplement is often just a waste of money, as it no longer delivers its full promised effect.

How to Tell If Your B12 Has Gone Bad

Visual and olfactory cues are the most reliable indicators that your B12 supplement has been compromised. You should immediately discard any supplement that:

Shows visible signs of mold or contamination. This is a clear indicator of moisture exposure and is unsafe to consume.
Has changed color. A change in the deep red color of many B12 supplements often signals chemical degradation.
Develops a strange or unusual odor. Any noticeable new smells could indicate that the product has gone off.
Has an altered texture or consistency. Clumping in a powdered supplement or a change in the form of a gummy are clear red flags.

The Importance of Proper Storage

To maximize the shelf life of your B12 supplements and ensure they maintain their potency, it is essential to follow correct storage procedures. The best practice is to keep them in a cool, dry, and dark place. Bedrooms and linen closets are often better choices than kitchens or bathrooms, which experience significant temperature and humidity swings. Always keep the lid on the original container tightly sealed and away from direct heat sources. If you use a supplement organizer, be sure to keep the bulk of the product stored optimally and only transfer what you need for the short term.

Conclusion: Prioritizing Potency over Shelf Life

While the answer to "can B12 go bad?" is that it doesn't become toxic like spoiled food, relying on an expired supplement for critical nutritional needs is a risky gamble. The loss of potency is a real and inevitable process hastened by exposure to light, heat, and moisture. For most people, consuming an expired vitamin will have no ill effect, but for those with a medical deficiency, it could hinder treatment and lead to serious health complications. For peace of mind and guaranteed effectiveness, the best course of action is to replace any expired B12 supplements and prioritize proper storage for all future purchases.

Sources and Additional Resources

For more information on vitamin B12 deficiency and supplementation, consult authoritative resources such as the NIH Fact Sheet for Health Professionals. It is always recommended to talk with a healthcare provider, especially for those with health conditions or on medications that may impact B12 absorption.

Frequently Asked Questions

No, expired B12 and most other vitamins do not become toxic or poisonous in the same way that food spoils. The primary issue is a gradual loss of potency, meaning the supplement becomes less effective over time.

Most vitamin supplements, including B12, have a typical shelf life of about two years from the date of manufacture. However, this can be affected by storage conditions.

While it's generally considered safe to consume expired B12 if it appears and smells normal, you risk not receiving the full dosage. For those addressing a deficiency, it is best to replace the supplement to ensure proper nutrient intake.

Key signs include mold growth, an unusual odor, or changes in the color and texture of the supplement. Any of these indicators mean the supplement has been compromised and should be discarded immediately.

Most B12 tablets and capsules do not need to be refrigerated and should be stored in a cool, dry place. However, some liquid drops or sublingual forms may require refrigeration; always check the manufacturer's specific storage instructions.

For optimal storage, keep B12 supplements in their original, tightly sealed container. Store them in a cool, dry, and dark location, away from direct sunlight, heat sources, and humidity.

If you have a diagnosed B12 deficiency, you should not rely on an expired supplement. The reduced potency means you may not be getting the therapeutic dose needed to correct the deficiency, which can have health consequences.