Are There Any Negative Side Effects to Taking Liquid Collagen?

November 2, 2025 •

4 min read

Over the past few years, collagen has surged in popularity as a beauty and wellness supplement, but what are the potential downsides? While generally considered safe for most users, it's crucial to understand the possible negative side effects to taking liquid collagen before incorporating it into your routine. This includes everything from mild digestive discomfort to more serious concerns like allergic reactions and heavy metal contamination.

Quick Summary

Liquid collagen can cause mild side effects such as digestive issues, including nausea, bloating, and diarrhea. Allergic reactions are also possible, particularly for those with sensitivities to the animal or fish sources. Some supplements may contain heavy metals due to a lack of FDA regulation, posing health risks.

Key Points

Digestive Upset: Common issues include bloating, gas, nausea, and changes in bowel movements, often dose-dependent.
Allergic Reactions: Individuals with allergies to fish, shellfish, or other animal products must check the collagen source to avoid allergic reactions.
Potential Contamination: Due to limited FDA regulation, some products may contain heavy metals, so third-party testing is a crucial indicator of safety.
Taste and Additives: Some liquid collagens have an unpleasant aftertaste, and added flavorings and preservatives can sometimes cause digestive problems.
Kidney Concerns: Those prone to kidney stones should be mindful of the oxalate content derived from excessive collagen intake.
Regulation Matters: The lack of government oversight on supplements means consumers must be diligent in researching and selecting reputable, transparent brands.

Potential Digestive Discomfort from Liquid Collagen

One of the most commonly reported negative side effects to taking liquid collagen is digestive upset. This can manifest in several ways, often beginning with mild symptoms that can become more bothersome with continued use.

Bloating and Gas: Some users experience feelings of fullness and excessive gas after consuming collagen, which can be attributed to the body adjusting to the new protein source.
Nausea and Stomach Pain: For some, taking liquid collagen can lead to stomach discomfort or nausea, particularly when taken on an empty stomach. This is often more prevalent with higher doses.
Diarrhea or Constipation: Collagen can affect gut motility in different ways for different people. Some experience diarrhea, while others may find themselves constipated. These issues may be related to the brand's specific formula or dosage.

How to Minimize Digestive Issues

If you experience digestive side effects, there are a few strategies you can try. Lowering your dosage, taking the supplement with food instead of on an empty stomach, or switching brands to see if a different formulation is more tolerable can help. If symptoms persist, it's wise to consult a healthcare provider.

Allergic Reactions and Food Sensitivities

Allergies are a more serious, though less common, concern with liquid collagen supplements. Since most collagen is sourced from animals (bovine, marine, or chicken), those with specific food allergies must be cautious.

Source-Specific Allergies: Individuals allergic to fish or shellfish should avoid marine collagen, as this can trigger a severe allergic reaction. Similarly, those with bovine or chicken sensitivities need to be careful with other common collagen sources.
Rare Skin Reactions: While exceedingly rare, there have been case reports of severe skin reactions, such as generalized bullous fixed drug eruption (GBFDE), associated with collagen supplements. Any spreading rash, blistering, or swelling should prompt immediate medical attention.

Unpleasant Taste or Odor

Some users report that liquid collagen can leave a lingering, unpleasant aftertaste or odor, often described as acidic or fishy, depending on the source. While this is not a health risk, it can make consistent daily use difficult. Many brands add artificial sweeteners and flavors to mask this, but these additives can sometimes contribute to digestive distress in sensitive individuals. Choosing a high-quality product with transparent sourcing can help mitigate this.

Contaminants and Lack of Regulation

One of the most significant concerns is the lack of regulation in the supplement industry, particularly in the United States, where the FDA does not review supplements for safety or efficacy before they are sold. This can lead to potential contamination.

Heavy Metals: Reports have found that some collagen supplements test positive for heavy metals like arsenic, lead, and cadmium. These substances can be harmful, especially with long-term exposure. It's crucial to choose brands that conduct and provide third-party testing results for purity.
Unlisted Ingredients: The lack of strict regulation means that a supplement may contain more or less of the stated ingredients, or even additional, unlisted additives that could cause side effects.

Potential for Kidney and Liver Concerns

While moderate collagen intake is generally safe for most healthy adults, excessive consumption could potentially cause issues for those with pre-existing conditions.

Kidney Stones: Collagen is rich in the amino acid hydroxyproline, which is converted to oxalate by the body. Excessive oxalate can contribute to the formation of kidney stones, especially in individuals with a history of them.
Liver Fibrosis: Though rare and linked to excessive intake, some studies have noted a correlation between too much Type I collagen and liver fibrosis in animal models, though the human impact is not fully clear.

Comparison of Collagen Supplement Formats

To illustrate the differences between various collagen forms and their potential side effects, consider the following table:


Feature	Liquid Collagen	Powdered Collagen	Capsule Collagen
Absorption Rate	Very high due to pre-hydrolyzed peptides.	Medium, improves with hot liquids.	Low, requires stomach acid for breakdown.
Ease of Use	Easy and convenient, ready-to-drink format.	Versatile; can be mixed into various foods and drinks.	Convenient for travel, no mixing required.
Dosing Flexibility	Pre-dosed, so less flexible.	Highly flexible, can be adjusted easily.	Limited dosage flexibility; may require multiple pills.
Additives	Often contains sweeteners, flavors, and preservatives.	Can be unflavored, with fewer additives.	Minimal additives, but capsule itself is an ingredient.
Common Side Effects	Digestive issues, potential allergens from additives.	Less likely to cause issues, but can have a chalky taste.	Slower absorption can lead to mild digestive upset.

Conclusion: Making an Informed Decision

Ultimately, whether the mild negative side effects to taking liquid collagen are a concern depends on your personal health and tolerance. For many, the benefits to skin, hair, and joint health outweigh the risks of minor digestive upset. However, those with pre-existing conditions or specific allergies must approach with caution. It is always recommended to choose a reputable brand that prioritizes transparency and third-party testing to minimize exposure to contaminants. If you experience adverse symptoms, consult your doctor to determine if liquid collagen is right for you.

Frequently Asked Questions

Yes, liquid collagen can cause mild digestive issues such as bloating, gas, nausea, stomach pain, or changes in bowel movements like diarrhea or constipation, particularly at higher doses or when taken on an empty stomach.

Yes, it is possible to have an allergic reaction. Since most collagen is derived from animal sources like fish or bovine, people with pre-existing allergies to these sources should be cautious and check the product's origin.

Because the supplement industry is not strictly regulated by the FDA, there is a risk of contamination. Some reports have found heavy metals in collagen supplements, which is why choosing brands with third-party testing is important.

Some users report an unpleasant aftertaste, which can be fishy or acidic depending on the collagen's source. Manufacturers often add flavors and sweeteners to mask this taste, which can sometimes lead to other mild side effects.

In individuals who are prone to kidney stones, excessive intake of collagen could increase the risk of stone formation. This is because collagen contains hydroxyproline, an amino acid that can convert to oxalate in the body.

To minimize side effects, start with a low dose, take the supplement with food, and ensure you are using a high-quality brand with third-party verification for purity. If issues persist, consider trying a different form of collagen or consult a doctor.

Liquid collagen is often hydrolyzed, meaning it's broken down into smaller peptides for better absorption. While marketing often emphasizes superior absorption, the form is less important than the quality and consistency of the collagen peptides themselves.