What Is Spirulina?

This blue-green algae's been studied for blood sugar control... and more

Spirulina is a blue-green algae from the genus Arthrospira ("arthro" roughly means "joint," and "spira" means "spiral").

The Aztecs in Mexico and people living in the Lake Chad area in Africa have used spirulina for centuries. Spirulina's usually cultivated from lakes or farmed in ponds.

Spirulina contains several nutrients: fat-soluble vitamins (A, E, and K), fatty acids (DHA, EPA), beta-carotene, and minerals. It's also a source of protein, but it lacks high enough levels of some of the amino acids that your body needs to function at its best (unless you have a medical condition where you need to avoid specific amino acids, like phenylketonuria or "PKU"). Since spirulina comes from bacteria (cyanobacteria), it may be considered a protein source for vegans.

It's also important to note that the B12 in spirulina is in a different form as "pseudovitamin B12" than the type typically absorbable by your body. You'll likely need to look elsewhere for your B12 needs, especially if you follow a vegetarian or vegan way of eating, which can be low in B12. Lower levels of B12 are also found in adults over 60. And why's B12 important? Because your body needs B12 to make red blood cells. And it's also crucial for brain and nerve cell development. Not getting enough B12 can cause tiredness, memory loss, depression, and even different types of anemia.

This article takes a closer look at spirulina's potential uses and the associated risks.

Dietary supplements are not regulated like drugs in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. Choose a supplement tested by a trusted third party, such as USP, ConsumerLab, or NSF, when possible. However, even if supplements are third-party tested, that doesn't mean they are necessarily safe for all or effective in general. Therefore, talking to your healthcare provider about any supplements you plan to take and checking in about potential interactions with other supplements or medications is important.

Supplement Facts

  • Active Ingredient(s): Phycocyanins, fatty acids, protein, vitamins, minerals
  • Alternate Name(s): Blue-green algae, dihé (Chadic language, Africa), tecuitlatl (Aztec)
  • Legal Status: “Grandfathered” dietary ingredient (legally marketed before 1994)
  • Suggested Dose: One gram per day (for six months) to 19 grams per day (for two months) have been used in clinical trials. However, there is no official suggested dosage for spirulina.
  • Safety Considerations: Allergy, heavy metals (lead, cadmium, arsenic, mercury), toxins (microcystins, other cyanobacteria)

Uses of Spirulina

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

Some people claim that spirulina has a range of health benefits. Scientists have studied, but not necessarily proven, spirulina's impact on different areas of health, including but not limited to the following:

We'll explore what the science says about spirulina's effectiveness for these health outcomes.

Antioxidant Capacity

According to a meta-analysis (a collection of research) of nine studies with a total of 415 people, spirulina increased superoxide dismutase (SOD) and total antioxidant capacity (TAC). The studies used anywhere from one to eight grams (g) of spirulina per day, a pretty extensive range. Many of the studies included in the analysis had a relatively small number of people, meaning they might not be able to tell us much. The strength of the effects was not earth-shattering and was generally more substantial when people took five grams of spirulina per day or more.

The conclusion? Getting antioxidants from our foods can help reduce some of the inflammation in our bodies. To amp up antioxidants in your diet, try including various nutrient-dense foods you can source and afford. These foods don't have to be organic. Whole grains, fruit, and vegetables help increase your body's antioxidant capacity and reduce inflammation. Just don't rely on spirulina alone.

Blood Pressure

Scientists did a meta-analysis (a collection of several research studies on a topic) of five randomized controlled trials that included 230 people to check spirulina's effects on blood pressure. The people in the different studies took anywhere from 1 to 8 grams of spirulina daily. The lengths of the studies were anywhere from two to 12 weeks, and many were pretty small, meaning they might not be able to tell us very much.

When the data were pooled (put together) and analyzed from these studies, the scientists said that spirulina lowered systolic blood pressure by about 4.59 millimeters of mercury (mmHg) and diastolic blood pressure by 7.02 millimeters of mercury. Systolic pressure (top number) measures the pressure in your arteries when your heart beats. Diastolic pressure (bottom number) measures the pressure your arteries experience between each heartbeat. The biggest blood pressure-lowering in the studies was already seen in people with high blood pressure.

The scientists also said more high-quality studies are needed before we can start recommending that everyone with high blood pressure needs to start eating spirulina.

Spirulina tablets and powder in bowls
pilipphoto / Getty Images

Blood Sugar Control

Have you ever gotten a jittery feeling after eating sugary food? That may mean your blood sugar levels are changing rapidly. This situation can be dire for people coping with type I or II diabetes, eating disorders (including diabulimia), and more.

Over time, blood sugar spikes that are left uncontrolled can lead to damage to your body. Worst case, in certain conditions like diabetes, that can look like having to surgically remove parts of your body (amputation), heart attacks, kidney failure, or stroke, which can lead to paralysis of parts of your body. While spirulina would not likely be able to correct severe damage from uncontrolled blood sugar over time, it has lowered blood sugar levels in human studies. And why? It could be its protein and fiber content, or phycocyanin can help to an extent with inflammation. Scientists are still figuring it out.

Fourteen studies with 510 people with metabolic syndrome were included in a meta-analysis of spirulina's effects on blood sugar and other outcomes. Metabolic syndrome is a collection of symptoms like high blood sugar, high blood pressure, high triglycerides, low HDL ("good cholesterol"), and increased waist circumference, which can create more severe health problems. And many included studies didn't have many people (lower statistical power). People took anywhere from one to eight grams of spirulina per day. Blood sugar and insulin levels were reduced in some of the studies after taking specific amounts of spirulina. More high-quality studies are needed before healthcare providers recommend spirulina to lower blood sugar and insulin levels.

Generally, working with a team that includes a registered dietitian nutritionist (RD or RDN), particularly a Certified Diabetes Care and Education Specialist (CDCES), can help you explore your eating, movement, medication habits, and more. RDs/RDNs can help you build your toolkit and capacity to avoid spikes in your blood sugar, which could help you feel better. Remember, managing blood sugar can be challenging, and you don't have to do it alone!


Unfortunately, very few well-conducted human studies have looked at spirulina's effects on cancer. There've been several studies on test tube cells or animals that aren't humans. However, more well-constructed studies looking at its impact on humans are needed.

Cholesterol Levels

Scientists conducted a meta-analysis of spirulina's effects on cholesterol levels that had seven controlled trials for a total of 522 total people. They found that spirulina reduced total cholesterol (by 46.76 milligrams per deciliter (mg/dL)), low-density lipoprotein (LDL by 41.32 milligrams per deciliter), and triglycerides (by 44.23 milligrams per deciliter). It also increased the "good" cholesterol or high-density lipoprotein (HDL by 6.06 milligrams per deciliter). Again, why did spirulina do this? We're not sure, but scientists think it may be due to its nutritional profile (fiber, fatty acids like DHA and EPA), antioxidant capacity, or a combination.

While healthcare providers cannot recommend spirulina for lowering your cholesterol, they can suggest working with a team that includes a registered dietitian nutritionist (RD or RDN) to help you explore your eating patterns, movement, and more. Registered dietitian nutritionists can help you build your toolkit and your capacity.

Liver Health

Spirulina has been studied for its effects on liver health in people with nonalcoholic fatty liver disease (NAFLD). However, the study was small (only 13 people). Using spirulina for NAFLD is inconclusive until researchers conduct more studies.

Metabolic Syndrome

Scientists have studied spirulina's effects on metabolic syndrome. Metabolic syndrome happens when you have high blood pressure, high blood sugar, high cholesterol, and excess fat around your waist (excess abdominal fat). Metabolic syndrome can negatively impact your health and increase your odds of heart attack, stroke, and type II diabetes.

One meta-analysis compiled data from 18 studies. It suggested that spirulina could help lower high blood pressure, high blood sugar, and high cholesterol, which are all parts of metabolic syndrome. It's important to note that while spirulina may impact these outcomes, essential issues include exploring your current overall way of eating, your movement (exercise), and other equally important issues like addressing your emotional health. Spirulina can't solve these serious issues.

Consider working with a team that includes a registered dietitian nutritionist (RD or RDN) and perhaps one that's a Board Certified Specialist in Obesity and Weight Management (CSOWM). RDs/RDNs can help you explore your eating, movement, medication habits, and more. It's important to note that obesity can be closely tied to the determinants of health and health disparities which are also essential to address. In addition, they can help you build your toolkit and capacity to help you feel better.


In a meta-analysis of five studies, scientists looked at spirulina's effects on weight management in people coping with obesity. Spirulina decreased weight in people with obesity by 4.55 pounds and in those who were overweight by 2.82 pounds. However, clinically speaking, this is not enough to make a solid recommendation for using spirulina for obesity treatment. Furthermore, it's important to note that obesity can be closely tied to the determinants of health and health disparities.

Other Uses

Spirulina has fat-soluble vitamins (like A, E, and K), beta carotene and minerals, protein, and phycocyanins (pigments that produce a blue color and have antioxidant effects). Phycocyanins have been used as a dye in many industries, including pharmacy, culinary, and cosmetics.

What Are the Side Effects of Spirulina?

An allergic reaction may be possible in those allergic to spirulina. Allergic reactions would include rash or swelling. If you experience side effects, stop using spirulina, and contact your healthcare provider immediately.

Common Side Effects

Spirulina is generally safe, but some people have reported the following with its use:

  • Allergy
  • Headache
  • Muscle pain
  • Sweating
  • Trouble sleeping

Severe Side Effects

While severe side effects from spirulina are rare, be aware that the following have occurred:

  • Anaphylaxis (severe allergic reaction)
  • Throat swelling

Immediately stop using spirulina if you experience severe side effects, and call your healthcare provider.


People with phenylketonuria (inability to process the amino acid phenylalanine) and individuals with other amino acid disorders (ex., classical homocystinuria (HCU), maple syrup urine disease (MSUD)) may need to avoid spirulina due to its high protein--and thus amino acid--content.

The safety of spirulina in pregnant or nursing people has not been established. Speak with your healthcare provider before using spirulina if you're pregnant, plan to get pregnant, or are breastfeeding.

Please don't give children supplements–including spirulina–without discussing this with their pediatrician first.

Spirulina can sometimes be contaminated with things like lead or other heavy metals (it grows in lakes, after all) or toxins.

Dosage: How Much Spirulina Should I Take?

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.

As a general guideline, don't use more than what's listed on your product's label. Manufacturer recommendations might vary. And there's no recommended "effective" dosage of spirulina. Avoid spirulina if you're allergic or sensitive to it or any of its ingredients.

Studies have used from one to 10 grams a day for up to six months to 19 grams of spirulina a day for up two months, with a relatively good safety profile in people with different conditions.

Again, please do not give supplements to children without first discussing this with their pediatrician.

What Happens If I Take Too Much Spirulina?

An upper limit or recommended intake is lacking for spirulina. Taking around 40 grams per day for an unknown period has been noted. Contact your healthcare provider for information if you believe you've taken too much spirulina.


Blood thinners: While there are only about 0.26 micrograms of vitamin K in each gram of spirulina, taking far larger amounts could theoretically impact the blood-thinning effects of some medicines like Jantoven (warfarin).

Immunomodulators: Little evidence exists to support avoiding the use of spirulina with immunosuppressive drugs or drugs that change how the immune system works (immunomodulators).

It is essential to carefully read a supplement's ingredient list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.

How to Store Spirulina

Store spirulina in a cool, dry place. Keep spirulina away from direct sunlight. Discard as indicated by the "use by" date on the packaging. Keep away from children and pets.

Similar Supplements

Chlorella (a green algae supplement) is somewhat similar to spirulina.

Frequently Asked Questions

  • Is spirulina the same as chlorella?

    No. Chlorella and spirulina are different species of algae, but they're both supplements.

  • What antioxidants does spirulina have?

    Spirulina has phycocyanins.

  • I am vegan. Could I get all my protein and B12 needs from spirulina?

    While spirulina has most of the amino acids that your body needs, it doesn't have enough of some of them. Try to eat a balanced, varied diet to meet your unique protein needs. The B12 in spirulina–pseudovitamin B12–is in a different form than the type that's typically absorbable by your body. You'll likely need to look elsewhere for your B12 needs.

Sources of Spirulina & What to Look For

Blue-green algae species used in spirulina supplements are typically Spirulina maxima, Spirulina platensis, or Aphanizomenon flos-aquae.

Just because a remedy is considered "natural" does not mean it is safe. Some "wild-crafted" spirulina products may have been grown in water contaminated with heavy metals (mercury, lead, arsenic, cadmium) or other pollutants. Opt for supplements produced in labs and certified by third-party authorities like the U.S. Pharmacopeia (USP), ConsumerLab, or NSF International.

As with all supplements, talking with your healthcare provider before using spirulina to decide if it's right for you is essential.

Spirulina Supplements

Spirulina is often sold as a powder. It's also available in capsule, tablet, and liquid form.


Spirulina is an edible blue-green algae. Some claim spirulina benefits health conditions like obesity, high blood pressure, and cancer.

Spirulina contains several vital nutrients, including fat-soluble vitamins (A, E, and K), fatty acids (DHA, EPA), beta carotene, and minerals. It's also a source of protein, but it lacks high enough levels of some of the amino acids that your body needs to function at its best (unless you have a medical condition where you need to avoid specific amino acids, like phenylketonuria or "PKU").

Spirulina has been studied in humans for several indications, like increasing antioxidant capacity, reducing blood pressure, blood sugar, and cholesterol levels, and addressing liver health (NAFLD), metabolic syndrome, and obesity.

Researchers have shown that spirulina has some effects on increasing antioxidant levels in the body and reducing blood pressure, blood sugar, and cholesterol levels. However, the most effective way to go about long-term change in these areas is by exploring and addressing your overall eating patterns and movement over time and your social connections, which can all profoundly affect your health and well-being. Working with a registered dietitian nutritionist (RD/RDN) is one option to achieve your nutrition and movement goals.

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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 Regina C. Windsor, MPH, RDN
Listen to yourself. Connect the dots. Find your people. Go have fun.

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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