Nutrition Diet: What Should You Not Take With Chlorella?

October 8, 2025 •

4 min read

As a microalga rich in nutrients, chlorella is often touted as a superfood, but it contains large amounts of vitamin K, which can interfere with certain medications. For anyone considering this green supplement, knowing what should you not take with chlorella is crucial for preventing potential health risks and adverse interactions.

Quick Summary

Chlorella can interact negatively with specific medications, including blood thinners, immunosuppressants, and photosensitizing drugs, due to its high vitamin K content and immune-boosting properties. Certain health conditions like autoimmune diseases also warrant caution.

Key Points

Blood Thinners: Avoid taking chlorella with warfarin due to its high vitamin K content, which can decrease the medication's effectiveness and increase clotting risk.
Immunosuppressants: Do not combine chlorella with immunosuppressive drugs, as its immune-stimulating effects can counteract the medication's purpose.
Photosensitizing Drugs: Chlorella can increase skin sensitivity to the sun, an effect amplified by photosensitizing medications.
Diabetics on Medication: Be cautious when combining chlorella with blood sugar-lowering drugs, as it can enhance their effects and cause hypoglycemia.
Autoimmune Conditions: People with autoimmune diseases should avoid chlorella because its immune-boosting properties could worsen their condition.
Monitor for Side Effects: Common side effects like diarrhea and gas often occur initially but typically subside with time. If they persist, consult a doctor.
Seek Medical Advice: Always consult a healthcare provider before adding chlorella, especially if you are on medication or have pre-existing health conditions.

Key Medications to Avoid with Chlorella

While chlorella is generally considered safe for most people, its powerful nutritional profile means it can interact with certain medications and medical conditions. The most significant risks arise from specific drug interactions that can either render medication ineffective or increase adverse side effects.

Blood Thinners (Anticoagulants)

Chlorella is an abundant natural source of vitamin K, a nutrient essential for blood clotting. This poses a serious risk for individuals taking anticoagulant medications, such as warfarin (Coumadin), which work by slowing down blood clotting. The high vitamin K content in chlorella can counteract the effects of warfarin, reducing its efficacy and potentially increasing the risk of dangerous blood clots. Anyone on blood-thinning medication should not take chlorella without consulting their healthcare provider, as blood work may need to be monitored and medication adjusted.

Immunosuppressants

Chlorella has demonstrated immune-stimulating properties, meaning it can boost the body's immune response. This is generally considered a health benefit, but it can be detrimental for individuals with a compromised or suppressed immune system. For patients taking immunosuppressant drugs—such as those undergoing organ transplants or managing autoimmune diseases—chlorella could reduce the effectiveness of their medication. Taking both could potentially trigger an unwanted immune reaction. Some medications that suppress the immune system include azathioprine (Imuran), cyclosporine (Neoral), and prednisone.

Photosensitizing Drugs

Photosensitizing drugs increase the skin's sensitivity to sunlight, raising the risk of sunburn, rashes, and blistering. Chlorella has been known to have a similar effect, increasing photosensitivity. Combining chlorella with these medications can amplify the risk of skin damage from sun exposure. If you are taking photosensitizing medication, wearing sunblock and protective clothing is recommended, and discussing chlorella supplementation with your doctor is advisable.

Blood Sugar-Lowering Medications

Studies suggest that chlorella may help lower blood sugar levels. For people with diabetes taking blood sugar-lowering medications, this can be a concern. When taken together, chlorella may increase the effects of the medication, potentially leading to hypoglycemia (dangerously low blood sugar). Monitoring blood glucose levels closely and consulting a doctor before combining the two is a necessary precaution.

Health Conditions Requiring Caution with Chlorella

Beyond drug interactions, certain pre-existing health conditions can be problematic for chlorella users.

Autoimmune Diseases: Because of its immune-stimulating properties, chlorella may not be safe for people with autoimmune conditions like lupus. The immune system boost could potentially exacerbate the condition.
Iodine Sensitivity: Some chlorella supplements can contain iodine. People with a known sensitivity or allergy to iodine should avoid chlorella to prevent an allergic reaction.
Weak Immune System: In individuals with a weakened immune system, there is a risk of harmful bacteria overgrowing in the gut. People with immunodeficiency should be cautious and seek medical advice.
Allergies to Molds: Chlorella might cause an allergic reaction in people who are also allergic to molds.
Pregnancy and Breastfeeding: While some sources suggest potential benefits, the safety of chlorella during pregnancy and breastfeeding is not fully established, so it is often recommended to exercise caution.

Chlorella vs. Spirulina: A Comparison of Interactions

It's important to differentiate between chlorella and another popular microalga, spirulina, as their interaction profiles can differ, particularly concerning vitamin K content.


Feature	Chlorella	Spirulina	Key Interaction Implications
Vitamin K	High amounts	Moderate amounts, but generally lower	Chlorella has a more significant impact on blood clotting, making it more likely to interact with warfarin.
Iodine Content	Can contain iodine	Can contain iodine, especially if grown in iodine-rich water	Both can be a concern for people with iodine sensitivity or thyroid issues.
Immune Effects	Immune-stimulating properties	Immune-stimulating properties	Both should be used with caution by those on immunosuppressants or with autoimmune conditions.
Photosensitivity	Can increase sun sensitivity	Less commonly associated with increased photosensitivity	Chlorella poses a higher risk when combined with photosensitizing drugs.

Safe Consumption and Common Side Effects

To minimize the risk of adverse effects, it is best to consult with a healthcare professional to determine appropriate use. Taking chlorella with meals can also aid digestion and reduce initial side effects like gas, bloating, and cramping. Choosing a quality supplement that specifies "broken cell wall chlorella" can also improve nutrient absorption.

Common side effects, particularly during the first week of use, may include diarrhea, nausea, and green-colored stools. For most people, these symptoms subside as the body adjusts. If side effects persist or worsen, it is best to discontinue use and consult a healthcare professional.

Conclusion: Navigating Chlorella Safely

Chlorella is a potent supplement with many potential health benefits, but its strong vitamin K content and immune-boosting properties necessitate caution. Understanding what should you not take with chlorella is the most important step for safe use. Individuals on blood thinners like warfarin, immunosuppressants, or photosensitizing drugs must consult a doctor before starting chlorella. Those with autoimmune conditions, iodine sensitivity, or weakened immune systems should also seek professional medical advice. By staying informed and communicating openly with your healthcare provider, you can safely explore the benefits of this unique superfood while mitigating potential risks.

For more detailed information on specific drug interactions, it's recommended to consult reliable sources such as the National Institutes of Health.

Frequently Asked Questions

Chlorella has been shown to potentially lower blood pressure, so if you are taking medication for high blood pressure, consult your doctor. Combining them could lower your blood pressure too much, requiring adjustments.

Yes, if you have a thyroid condition, you should exercise caution. Some chlorella supplements contain iodine, which can affect thyroid function. It is best to consult an endocrinologist before starting chlorella.

There is currently no reliable information or reported interactions between chlorella and oral contraceptives. However, to be safe, discuss any supplements with your healthcare provider.

Chlorella is often used for detoxification. While generally safe, combining multiple detoxifying supplements without medical supervision is not recommended, as it can put a strain on the body's systems.

Initial side effects like diarrhea, nausea, or gas are common when starting chlorella. Taking it with food may help. If problems continue, stop use and see a doctor.

It is generally safe to take chlorella with a multivitamin. However, since chlorella is already very nutrient-dense, it's wise to ensure you're not getting an excessive intake of certain fat-soluble vitamins or minerals, especially vitamin K.

There is a lack of scientific studies confirming the safety of chlorella for children. It's recommended to avoid giving it to children unless under the specific guidance of a pediatrician.

While chlorella is an algae and not a shellfish, some individuals with shellfish allergies have reported allergic reactions to chlorella. Exercise caution and consult a healthcare provider if you have this allergy.

Yes, chlorella has been reported to make skin more sensitive to sunlight, which can increase the risk of sunburn or rashes. Using sun protection is advised.