How long can you store vitamin C?

October 28, 2025 •

4 min read

Most vitamin C supplements have a shelf life of about two years, though their potency can degrade significantly over time, especially when not stored correctly. As a notoriously unstable vitamin, factors like light, air, and heat play a huge role in determining how long can you store vitamin C effectively before it loses its benefits.

Quick Summary

The storage duration for vitamin C varies based on form and conditions. Supplements typically last up to two years, while serums degrade faster. Proper storage away from heat, light, and air is key to preserving potency. Look for color and texture changes as signs of oxidation.

Key Points

Supplements vs. Serums: Most vitamin C supplements can last up to two years, but serums degrade much faster after opening, typically lasting only 3 to 6 months.
Oxidation is the Enemy: Vitamin C is highly unstable and loses potency primarily due to oxidation caused by exposure to light, heat, and air.
Storage is Critical: To preserve potency, store vitamin C in a cool, dry, and dark place in an airtight, opaque container.
Identify Degradation: Watch for color changes (clear to yellow/brown), unusual smells (sour, metallic), and texture changes (clumping, graininess).
Expired = Ineffective: Using expired vitamin C is not harmful, but it offers reduced potency and may not provide the desired health or skincare benefits.

Understanding the instability of vitamin C

Vitamin C, or ascorbic acid, is a powerful antioxidant, but it's also highly unstable and sensitive to environmental factors. This instability means that its potency can diminish over time, even before its expiration date. The main culprit behind vitamin C degradation is oxidation, a chemical process that occurs upon exposure to oxygen, heat, and light. Just like a cut apple turns brown when exposed to air, vitamin C oxidizes into a less effective form, dehydroascorbic acid. The speed of this process is influenced heavily by the product's form and storage conditions.

Shelf life varies by product type

How long can you store vitamin C depends heavily on whether it's a dietary supplement or a skincare product, and what form it takes. Manufacturers typically set a conservative expiration date to guarantee full potency, but the actual shelf life can be influenced by consumer-level storage.

Dietary Supplements

Tablets and Capsules: These generally have the longest shelf life, often up to two years, due to their protective casing that minimizes exposure to light and air.
Chewables and Gummies: The added moisture and sugars in these forms make them more susceptible to degradation. They may lose potency faster than tablets.
Powdered Form: Powdered vitamin C can be stable for extended periods if kept completely dry and airtight. However, moisture exposure can lead to clumping and degradation.

Skincare Serums

Opened Serums: Once a bottle is opened, exposure to air significantly reduces its shelf life. Many serums should be used within three to six months to ensure maximum efficacy.
Unopened Serums: An unopened, well-packaged vitamin C serum might last for a year or more, provided it is kept in optimal conditions.

Optimizing storage to extend potency

Proper storage is the most effective way to maximize the shelf life and effectiveness of vitamin C products. The goal is to minimize exposure to its primary enemies: heat, light, air, and moisture.

Best practices for vitamin C storage

Choose a Cool, Dry Location: Avoid storing vitamin C in a humid bathroom cabinet or a hot kitchen. A bedroom drawer, closet, or pantry is a much better option.
Keep It Out of Sunlight: Always store vitamin C away from direct sunlight. Opaque containers are superior to clear ones for blocking UV light.
Seal Containers Tightly: After each use, ensure the cap is securely fastened to limit air exposure, which causes oxidation. For serums, pump applicators are often better than dropper bottles for this reason.
Consider Refrigeration: For certain liquid formulations, refrigeration can significantly slow the oxidation process. Always check the label for specific recommendations.
Avoid Bulk Buys: Unless you use vitamin C frequently, buying smaller quantities can prevent you from having an unused product lose its potency before you can finish it.

Recognizing expired vitamin C

As vitamin C degrades, it undergoes visible and sensory changes. If you notice any of these signs, it's a good indication that the product is past its prime and should be discarded.

A comparative guide to expired vs. fresh vitamin C


Characteristic	Fresh Vitamin C	Expired / Oxidized Vitamin C
Appearance	White to faint yellow powder or clear/straw-colored liquid	Yellow, brown, or orange discoloration
Texture	Fine powder, smooth liquid	Clumpy or hard powder, grainy or thicker liquid
Smell	Little to no scent, sometimes slightly sharp	Sour, metallic, or 'off' odor
Efficacy	Full potency, delivers antioxidant benefits	Reduced effectiveness; minimal or no benefits

Can you use expired vitamin C?

While it's generally not harmful to ingest or apply expired vitamin C, it is a waste of money and will not provide the intended benefits. An oxidized vitamin C serum may even become irritating to the skin. For individuals using vitamin C to address specific deficiencies, relying on an expired supplement is unwise, as it will not provide the necessary dosage.

Conclusion: Prioritize fresh and proper storage

To get the most value and health benefits from vitamin C, the key is to prioritize freshness and proper storage. While most supplements have a shelf life of around two years, this is only a manufacturer's guarantee of potency, not a certainty. By following best practices—keeping products cool, dark, and airtight—you can significantly slow down the degradation process. Always be vigilant for signs of oxidation, and if a product seems compromised, discard it. By treating this powerful but sensitive nutrient with care, you can ensure you receive its full antioxidant power and effectiveness for as long as possible.

For more information on the chemical stability of vitamin C in various food matrices and storage conditions, see this academic study: Stability of vitamin C in fresh and freeze-dried capsicum stored at different temperatures.

Frequently Asked Questions

Yes, vitamin C is notoriously unstable and loses its potency over time, especially with exposure to light, heat, and air. This process, known as oxidation, converts the active ascorbic acid into a less effective form.

While generally safe to consume, expired vitamin C is not recommended. Its potency will be significantly reduced, meaning you won't get the full, labeled dose and the supplement may be ineffective for your health needs.

Using an expired vitamin C serum is unlikely to be beneficial as it has lost its potency. In some cases, oxidized serums can cause skin irritation or worsening of certain skin conditions instead of improving them.

The best practice is to store vitamin C supplements in a cool, dry, and dark place, such as a closet or pantry. Keep them sealed tightly in their original opaque container to minimize exposure to light, air, and moisture.

Signs of oxidation include a change in color (e.g., from clear to yellow or brown), a change in texture (like thickening or clumping), or a new, unpleasant smell (e.g., sour or metallic).

For some unstable liquid formulations, storing vitamin C serum in the refrigerator can help slow down the oxidation process and extend its shelf life. Always check the product's specific storage recommendations.

Yes, the form of vitamin C impacts its shelf life. Tablets and capsules, being more protected, generally last longer than chewables or gummies. Powdered forms can last a long time if kept completely dry, while liquid serums have the shortest shelf life once opened.