What Happens if You Take Probiotics That Have Gone Bad?

October 10, 2025 •

4 min read

While many people worry about the safety of consuming expired dietary products, research suggests that expired probiotics are primarily less effective, not harmful, for most healthy individuals. So, what happens if you take probiotics that have gone bad? The primary concern isn't illness, but rather a lack of intended benefit.

Quick Summary

Consuming expired probiotics for a nutrition diet is generally safe for healthy people but is unlikely to provide the intended benefits as the live bacteria count decreases over time, especially with improper storage.

Key Points

Ineffective, Not Harmful: For most healthy people, the main risk of taking expired probiotics is a loss of potency and a waste of money, not a serious health threat.
CFU Count Decreases: The live, active bacteria (Colony-Forming Units or CFUs) in probiotics die off over time, making the supplement less effective past its expiration date.
Risks for Vulnerable Groups: Immunocompromised individuals, those who have undergone recent surgery, or those with catheters face a rare but heightened risk of infection from probiotics.
Check for Spoilage: Visibly spoiled probiotics (unusual smell, color, or texture) should be discarded immediately, regardless of the expiration date, as this could indicate contamination.
Proper Storage is Essential: Storing probiotics away from heat, humidity, and light, and adhering to refrigeration instructions, is critical for maximizing their shelf life and efficacy.

Expired or 'bad' probiotics typically pose a greater risk to your wallet than your health, but understanding the difference between a product that has simply lost potency and one that has truly spoiled is crucial. The effectiveness of probiotics hinges on the number of live microorganisms they contain, measured in Colony-Forming Units (CFUs). Over time, these live bacteria naturally die off, especially if stored improperly, making the product less potent and ultimately ineffective.

The Difference Between Expired and Spoiled

An expired probiotic is past its "best by" or expiration date, meaning the guaranteed CFU count on the label is no longer valid. The product is not dangerous, but simply less effective than when it was fresh. In contrast, a spoiled probiotic is one that has been compromised, likely due to improper storage exposing it to heat, moisture, or light. This could potentially introduce unwanted contaminants. A visual or sensory check can often help distinguish between the two, though it's not foolproof.

Efficacy vs. Safety: The Primary Outcome

For the average, healthy person, the most common outcome of taking expired probiotics is a simple waste of money. Research has shown that while many expired products still contain some live bacteria, the number is often significantly lower than the effective dose required for a noticeable health benefit. The best case scenario is that nothing happens; the worst is that you experience some mild, temporary digestive discomfort as your body adjusts to the non-viable or lower bacterial load.

Health Implications for Vulnerable Individuals

While low-risk for most, certain individuals should exercise caution. Probiotics carry a rare but potential risk of causing infections in people with compromised immune systems, those with venous catheters, or those who have recently undergone surgery. For these groups, there is a remote possibility that bacteria or yeast from a supplement could enter the bloodstream. Furthermore, rare but tragic cases of contamination in supplements have occurred, highlighting the unique risks associated with products containing live organisms. Therefore, if you fall into any of these categories, it is best to avoid expired or improperly stored probiotics and always consult a healthcare provider.

Mild Side Effects in Sensitive Individuals

Even with fresh, effective probiotics, mild digestive side effects like gas and bloating can occur as the gut microbiome adjusts. This can also happen with expired or weakened products, especially in those with sensitive digestive systems. Some individuals may also experience headaches, particularly those sensitive to histamines, as certain probiotic strains in fermented products can produce these biogenic amines.

Identifying Probiotics That Have Gone Bad

Check the expiration date: This is the most reliable indicator of potency. If the date has passed, assume the CFU count is diminished.
Conduct a sensory check: If your probiotic capsules or powder have an unusual smell, have changed color, or appear to be clumped or discolored, discard them immediately. This may indicate moisture contamination or spoilage.
Assess efficacy: If you notice a decline in the benefits you typically experience, it could be a sign that the probiotic is no longer potent.

Storing Probiotics for Maximum Potency

Proper storage is the best way to ensure the viability and effectiveness of your probiotic supplements. Follow the label instructions precisely, and adhere to these guidelines:

Check for refrigeration requirements: Some probiotics need to be refrigerated, while others are shelf-stable. Don't assume; check the label.
Avoid heat and humidity: Keep all probiotics in a cool, dry place away from direct sunlight, ovens, or humid bathrooms. Heat and moisture can kill the bacteria.
Keep in original packaging: Blister packs or dark glass bottles protect probiotics from environmental factors better than a weekly pill organizer.

Comparison: Probiotic Supplements vs. Fermented Foods


Feature	Probiotic Supplements	Fermented Foods (e.g., yogurt, sauerkraut)
Strain Specificity	Contain specific, targeted strains often supported by clinical trials.	Contain diverse, but less specific, combinations of bacteria and yeast.
Potency	Can be formulated with a high CFU count, though potency can diminish with time.	Can contain a very high bacterial count, sometimes higher than supplements.
Convenience	Shelf-stable options are portable; easier for targeted, daily dosing.	Requires consistent refrigeration and can be less practical for travel.
Shelf Life	Clearly marked expiration date; can last 1-2 years if stored correctly.	Varies greatly; depends on the food type and storage conditions.

Conclusion: Prioritize Freshness and Safety

When it comes to probiotics, freshness equals potency. While taking an expired supplement is unlikely to cause significant harm, it is an ineffective use of your resources. The live bacteria you purchased for a specific health benefit have likely dwindled to an ineffective level. For safety, always discard probiotics that show any signs of spoilage, such as unusual odors or textures. For those with compromised immune systems, the risk of contamination is real, and expert medical advice should always be sought. By following proper storage instructions and being mindful of expiration dates, you can ensure you get the most value and health benefits from your probiotic intake.

For more information on the safety of dietary supplements, visit the National Institutes of Health (NIH) website for fact sheets on probiotics.

Frequently Asked Questions

For most healthy individuals, expired probiotics are highly unlikely to make you sick. The live bacteria lose their potency over time, meaning the supplement becomes ineffective, but it typically does not harbor dangerous pathogens.

The most reliable sign is the expiration date on the packaging. Additionally, look for any unusual smells, colors, or clumping in the product, as these are signs of spoilage due to moisture or heat.

If a probiotic has an off or unusual smell, it should be discarded immediately. This is a sign that moisture has likely compromised the product, and it may be spoiled and contaminated, making it unsafe to consume.

No, not all probiotics need refrigeration. Many are shelf-stable and can be stored at room temperature. Always check the label for specific storage instructions, as this varies by product and bacterial strain.

Common side effects, particularly when starting a new supplement, can include mild digestive issues like gas, bloating, or diarrhea. These typically resolve as your body adjusts.

Both have benefits. Fermented foods offer a wider diversity and potentially higher concentration of bacteria, while supplements provide specific, targeted strains in a measured dose. Using both can be beneficial for overall gut health.

Probiotics contain living organisms that are sensitive to environmental factors. Exposure to heat, moisture, and light can accelerate the death of these beneficial bacteria, reducing the supplement's effectiveness and shelf life.