What Is Chlorella?

A supplement that may lower high cholesterol

Chlorella is a bright green algae. Chief among chlorella's benefits is that it may help prevent the kind of cell damage that increases your risk of diabetes, heart disease, Alzheimer's disease, and certain cancers. This is thanks to its high levels of antioxidants like vitamin C, omega-3 fatty acids, and carotenoids like beta carotene, which combat free radicals.

Chlorella is also considered a "superfood" because it is high in protein, iron, dietary fiber, B vitamins, and complex carbohydrates. These nutrients may help prevent iron deficiency during pregnancy. Chlorella can also treat high cholesterol, menstrual cramps, fibromyalgia, and depression, although the scientific evidence supporting these claims is lacking.

This article describes chlorella's uses and benefits as a dietary supplement as well as its possible risks, side effects, and interactions.

Dietary supplements are not regulated in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement that has been tested by a trusted third party, such as USP, ConsumerLab, or NSF.

However, even if supplements are third-party tested, that doesn't mean they are necessarily safe for all or effective in general. It is important to talk to your healthcare provider about any supplements you plan to take and to check in about any potential interactions with other supplements or medications.

Supplement Facts

  • Active ingredient(s): Beta carotene, chlorophyll, lycopene, lutein
  • Alternate name(s): Bulgarian green algae
  • Suggested dose: No guidelines available; research doses range from 1 to 6 grams daily
  • Safety considerations: May contain iodine, high vitamin K content (see Interactions)

What Are Chlorella's Uses?

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or doctor. No supplement is intended to treat, cure, or prevent disease.

Chlorella is a good source of many nutrients, such as protein, iron, fiber, carbohydrates, antioxidants, and more. Because of its nutritional content, some claim that it can treat a range of health conditions. However, there is not enough evidence to support most of its claims.

Below are a few possible uses of chlorella.

Lowers High Cholesterol

High cholesterol is a risk factor for heart disease. Diet modifications are recommended for reducing cholesterol levels when they're high. Medications are also often prescribed to treat high cholesterol levels. However, there is much interest in alternative ways to reduce cholesterol.

Chlorella has been studied as cholesterol-lowering aid.

According to a 2014 study published in Nutrition Journal, a daily 416-milligram (mg) dose of chlorella improved blood lipid levels in 62 adults with moderately elevated cholesterol. Not only were there reductions in total cholesterol, triglycerides, and LDL ("bad") cholesterol, but there were also increases in HDL ("good") cholesterol.

A meta-analysis published in 2018 found that taking 4 grams (g) of chlorella supplementation daily for at least eight weeks significantly reduced total cholesterol, LDL cholesterol, blood pressure, and blood sugar compared to a placebo.

A more recent trial published in 2021 found that smaller doses (1,500 mg per day) in people with diabetes positively affected lipid profiles and blood sugar levels.

Another meta-analysis published in 2022 concluded that chlorella supplementation reduced total and LDL cholesterol but did not improve triglycerides or HDL cholesterol. This took effect at 1,500 mg per day, whereas higher doses had no effect.

More research is necessary before recommending chlorella supplementation for high cholesterol. Consult your healthcare provider first before starting any supplement.

Reduces Anemia Risk During Pregnancy

Iron requirements increase during pregnancy, sometimes leading to anemia if the pregnant person becomes iron-deficient. Chlorella happens to be a great source of iron.

In a 2010 study in the journal Plant Food for Human Nutrition, researchers in Japan provided 70 pregnant people with either a daily 6 g (6,000 mg) dose of a chlorella supplement or a placebo. Treatment started from 12–18 weeks of gestation and continued until delivery.

When compared to the placebo group, the people in the study who took the chlorella had significantly higher hemoglobin levels during their second and third trimesters. Low hemoglobin levels can indicate the possibility of an anemia diagnosis.

Interestingly, those who took the chlorella also had a lower incidence of edema (tissue swelling), proteinuria (protein in urine), and gestational hypertension (high blood pressure).

Chlorella may be useful in lowering cholesterol levels, but further research is necessary to determine efficacy and the appropriate dose. Chlorella is also a good source of iron for those at risk of iron deficiency anemia.

Side Effects of Chlorella

Chlorella is generally considered safe and well tolerated. That said, chlorella can cause side effects, especially during the first few weeks of treatment. These include:

  • Stomach cramps
  • Nausea
  • Gas
  • Diarrhea
  • Green stool

Additionally, some have reported allergic reactions, including asthma and anaphylaxis.

Most of these side effects tend to resolve as your body adapts to treatment.

Chlorella may also cause photosensitivity, increasing the risk of sun rash and sunburn. To help mitigate this effect, wear plenty of sunscreen and avoid excessive sun exposure.


Chlorella is not expected to cause adverse effects in a breastfed infant. However, it can cause breast milk to turn green. If you are breastfeeding or plan to breastfeed, it is best to consult a healthcare provider about chlorella use.

Chlorella's safety for children has also not been established.

People allergic to mold may also be allergic to chlorella. To be safe, take a smaller "test" dose of chlorella and wait 24–48 hours to see if any allergy symptoms develop. The same concerns apply if you have an iodine allergy because chlorella is especially high in iodine.

Chlorella can also cause bad reactions in people with thyroid disease given that excess intake of iodine can worsen hyperthyroid symptoms or cause an "iodine crash" in people with hypothyroidism.

 Verywell / Anastasia Tretiak

How to Take Chlorella

There are no guidelines for the appropriate use or amounts of chlorella to take.

Common daily intake orally ranges from 3 g to 10 g.

Never exceed the dose the manufacturer recommends. If anything, start with the smallest possible dose and increase it gradually. Doing so may help you avoid gastrointestinal side effects.

Tablets are the easiest form of chlorella to take because the dose remains controlled and consistent. If taking it as a powder or liquid, stick to exact measurements to avoid underdosing or overdosing.

Chlorella powder can be mixed with water, juice, yogurt, and smoothies, but be aware that it has a slightly seaweedy smell and flavor. Some find that adding it to vinaigrette dressings, miso soups, stir-fries, or wheatgrass can conceal its smell and taste. Cooking chlorella does not diminish its nutritional value.

What Happens if I Take Too Much Chlorella?

There is not much information on chlorella and dosing, but you may be more likely to experience side effects when taking too much.


Chlorella contains high amounts of vitamin K, which can promote blood clotting and reduce the efficacy of blood thinners like Jantoven (warfarin). If your healthcare provider prescribes warfarin, talk with them about any supplements you are taking (or planning to take), including chlorella. The healthcare provider should order blood tests to monitor how well the warfarin is working and may make adjustments to the dose if necessary.

Chlorella may amplify the effects of any photosensitizing medications (drugs that increase sensitivity to sunlight), putting you at a greater risk of sunburn. Be sure to use sunscreen or stay out of the sun.

How to Store Chlorella

Follow the manufacturer's instructions on the product label for storage. Always store out of reach of children.

Similar Supplements

Spirulina and kelp are two other popular algae-based supplements.

Spirulina is a blue-green algae that contains nutrients, including fat-soluble vitamins, beta carotene, and minerals.

Kelp is a type of brown seaweed that typically grows in underwater forests. It provides nutrition for sea life but is also a food staple for humans. As a supplement, it often serves as a source of iodine.

Sources of Chlorella and What to Look For

Chlorella is mostly available in supplement form in the United States. You can readily source it online as well as in many natural food stores and shops specializing in dietary supplements.

Tablets are the easiest form of chlorella to take because the dose remains controlled and consistent. If taking it as a powder or liquid, use exact measurements to avoid underdosing or overdosing.

To ensure quality and safety, opt for brands that have been tested and certified by an independent body like the U.S. Pharmacopeia (USP), ConsumerLab, or the National Science Foundation (NSF). Contamination often occurs with algae-based ingredients. The presence of a USP, NSF, or ConsumerLab seal tells you the product was tested for the presence of contaminants, such as arsenic and lead, and that none were found.

One type of algae, called Aphanizomenon flos-aquae, is known to contain toxins and is best avoided.

Though you may be tempted to buy the "real" chlorella from Asia, doing so requires caution. If you cannot read the language on the product label, you can never know for sure what other ingredients may be in the supplement (or what ingredients may be missing from it).

A study by the National Center for Complementary and Integrative Health found that Chinese herbal remedies are sometimes contaminated with pesticides, heavy metals, drugs, and undeclared animal and plant products.


Chlorella is an algae-based supplement rich in vitamins, minerals, fiber, and antioxidants. It is often promoted as a good source of these nutrients for people who don't consume adequate fruits and vegetables in their diet. However, research does not support many of the promoted health benefits of chlorella.

A diet that provides at least five servings of fruits and vegetables daily will provide many of the vitamins, minerals, fiber, and antioxidants that you need. You should not consider green powders and algae-based supplements an alternative to a diet rich in fruits and vegetables.

Frequently Asked Questions

  • Does chlorella help to alkalinize the body?

    Though marketing uses this term to promote products, no food or beverage can significantly change your blood's pH level (pH refers to whether a substance is acidic, alkaline, or neutral). The idea that many foods we eat in our diet are acidic and can lead to disease is theoretical and not based on evidence. Our lungs and kidneys are involved in tightly regulating blood pH no matter what we eat. An abnormal pH level in your blood is not desirable and can lead to further health concerns.

  • Can chlorella help to reduce symptoms associated with fibromyalgia?

    Some preliminary (early) evidence indicates that chlorella supplementation can help to reduce pain symptoms associated with fibromyalgia. In one study, a combination of chlorella tablets and liquid extract helped to reduce pain symptoms when compared to a placebo. More research would help to determine the best form of supplement and appropriate doses. Be sure to talk with your healthcare provider if you are considering using chlorella.

  • Is chlorella supplementation good for your liver?

    Some preliminary (early) evidence suggests that chlorella supplementation reduced liver enzymes and markers of inflammation (compared to placebo) in people with non-alcoholic fatty liver disease (NAFLD). Further research is still necessary. If you are considering chlorella supplementation, discuss the pros and cons with your healthcare provider first.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Jennifer Lefton, MS, RD/N, CNSC, FAND
Jennifer Lefton, MS, RD/N-AP, CNSC, FAND is a Registered Dietitian/Nutritionist and writer with over 20 years of experience in clinical nutrition. Her experience ranges from counseling cardiac rehabilitation clients to managing the nutrition needs of complex surgical patients.

Originally written by Cathy Wong
Cathy Wong

Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.

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