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Printed from https://bottledhope.co/supplements/spirulina/. Last reviewed 2026-09-25. Check the site for the latest version.

Spirulina

A dried blue-green alga sold as a supplement and added to foods. A US government database lists hay fever, high blood pressure and diabetes among its uses.

Explained simply · Last reviewed

What it is

Spirulina is a dried blue-green alga, sold as a supplement and added to foods. LiverTox, the US government's liver-injury database, says it grows in warm, highly alkaline lakes, and that the people of Mexico and Central America have eaten it for centuries. It says spirulina is used as a food and as a supplement for conditions including hay fever (allergic rhinitis), high blood pressure, diabetes, stress, fatigue, anxiety and depression, and to counter unintended weight loss.

More about Spirulina

LiverTox, the US government's liver-injury database, says it grows in warm, highly alkaline lakes, and that the people of Mexico and Central America have eaten it for centuries. It says spirulina is used as a food and as a supplement for conditions including hay fever (allergic rhinitis), high blood pressure, diabetes, stress, fatigue, anxiety and depression, and to counter unintended weight loss.

A 2025 review of spirulina trials says spirulina is mainly Arthrospira platensis and Arthrospira maxima. It adds that the genus has since been renamed Limnospira, and that "spirulina" is a commercial name. LiverTox classes these blue-green algae as cyanobacteria. A 2024 review of spirulina allergy says spirulina also grows wild in Lake Chad in central Africa, where people collected it and added the dried alga to their cooking.

LiverTox says spirulina is rich in protein, vitamins and minerals, and that it also contains beta-carotene and a blue-green pigment, phycocyanin, which has been proposed as its active ingredient. The 2024 review says it is sold as tablets, capsules and powder, and is added to foods such as snacks, pasta and bread.

Also known as: Arthrospira platensis, Arthrospira maxima, Limnospira

At a glance

Safety: known risks, 2 groups who should avoid it or take extra care and 1 documented interaction. See Safety ↓

Claims made about Spirulina, and how strong the evidence is for each:

Each rating follows our published rules and the sources cited for it. We don’t add our own medical judgment. How we rate

Safety

Read this before the ratings below.

Risks

  • LiverTox, a US government liver-injury database, rates spirulina a possible rare cause of clinically apparent liver injury (its likelihood score D). It reports one published case, in which jaundice appeared five weeks after starting spirulina in a man who was also taking other medicines that can harm the liver; he recovered fully once all of them were stopped.
  • LiverTox also reports several cases sent to national adverse-event registries. Across the reports, severity ranged from mild rises in liver enzymes to hepatitis that cleared on its own, with no reports of acute liver failure. LiverTox states that the role of spirulina, as opposed to other herbal components or contaminants, has not been shown, and that liver injury due to spirulina “must be very rare if it occurs at all”.
  • LiverTox states that spirulina typically grows in warm open lakes and “can be contaminated with other blue-green algae that produce toxins (microcystins)”. It names contamination with microcystins as a possible explanation for the liver-injury reports, and states that the purity of the products implicated has not been reported. A 2021 review states that studies have found spirulina products with “contamination of toxic substances—cyanotoxins, heavy metals, or polycyclic aromatic hydrocarbons (PAHs)”. A 2023 review names heavy metal levels, which depend on where the algae grew, as a concern, and cites one analysis of commercial supplements that did not find levels above regulated limits.
  • A 2024 review found four published case reports, describing five people in Europe, of allergic reactions after taking spirulina tablets or powder. It classed four of the five reactions as anaphylaxis, a severe whole-body allergic reaction. Three of the five needed hospital care, and one needed an adrenaline (epinephrine) injection. The review states that spirulina allergy is not commonly reported or diagnosed, and notes “a notable absence of epidemiological studies on hypersensitivity to spirulina”.
  • On the trials themselves, a 2025 review reports “no serious adverse events” in the studies it included, and another 2025 review reports that none of its included studies reported adverse effects. LiverTox states that in controlled trials spirulina has not been linked to rises in liver enzymes, and that “Studies have found it to be safe without significant adverse events.” It reports that a US Pharmacopeia safety review concluded that spirulina should be considered safe, but that prospective studies of its safety were warranted.

Who should avoid it or take extra care

  • People with phenylketonuria or maple syrup urine disease, or others who must limit protein or particular amino acids: a 2023 review, citing a US Pharmacopeia safety review, states that “due to the presence of considerable protein and amino acid amounts, Spirulina should be used with caution in patients with protein or amino acid limitations such as phenylketonuria or maple syrup urine disease”.
  • People with a history of allergy to algae: the same 2023 review states that spirulina “should be used with caution”.

Documented interactions

  • Immunosuppressive drugs: A 2023 review states that “it has been reported in a few documents” that taking spirulina with immunosuppressive drugs is not recommended, because of its effects on the immune system. Source [1]

Safety sources: Source [1]Source [2]Source [3]Source [4]Source [5]Source [6]

What the evidence says

Each claim is rated on its own evidence. Ratings follow the scale on our methodology page.

  • Improves blood cholesterol and triglyceride levels Evidence rating: Limited

    People take it hoping it will improve their cholesterol and triglyceride levels.

    Two reviews found lower cholesterol and triglycerides and higher HDL cholesterol, and a third found no significant change; the graded reviews disagree on how sure they are: high to very low certainty.

    These reviews measured cholesterol and triglyceride levels in the blood, not heart attacks or strokes, and they disagree. A 2025 meta-analysis pooled 13 trials for each lipid measure in adults with overweight or obesity. Some of them also had type 2 diabetes, high blood pressure or other conditions. The review found that, compared with control groups, spirulina lowered total cholesterol, triglycerides and LDL cholesterol and raised HDL cholesterol.

    The 2025 review rated certainty moderate for LDL cholesterol, low for total cholesterol and triglycerides, and very low for HDL cholesterol. It reported substantial differences between trials (I² 74% to 86%). The HDL result was no longer statistically significant when any one of three trials was left out. The review also included trials that were not randomized.

    A 2023 meta-analysis of 20 trials reported the same four changes and rated certainty high for all of them. It also reported large differences between trials (I² 82% to 97%) and, for HDL cholesterol, significant publication bias. Its trials included people with diabetes, fatty liver disease, HIV or high blood pressure. Two gave spirulina in a sauce, one combined it with exercise and one with the diabetes medicine metformin.

    A 2025 meta-analysis of spirulina and chlorella trials found no statistically significant difference in cholesterol or triglycerides with spirulina. Two of its authors are employed by the company Sea4Us. LiverTox, a US government database last updated for spirulina in 2019, states: “There have been limited studies in humans, but it has not been proven to be effective in treating any medical condition.”

    Under this site’s rules, when sources disagree the lower rating is taken. The lowest certainty the graded reviews give these outcomes is very low.

    Sources: Source [1]Source [2]Source [3]Source [4]

  • Lowers blood sugar Evidence rating: Limited

    People take it hoping it will bring their blood sugar down.

    The one graded review found no significant difference in fasting blood sugar or insulin, and rated that evidence very low certainty.

    The one graded review cited here found no statistically significant difference, and rated that evidence very low certainty. This 2025 meta-analysis of adults with overweight or obesity compared spirulina with control groups. It measured fasting blood glucose (nine trials) and insulin (four trials), and rated certainty for both very low.

    Its authors point to high heterogeneity (large differences between trials), very low certainty and wide confidence intervals, and call for high-quality studies. They report that one earlier meta-analysis also found no significant improvement. They add that others, in people with type 2 diabetes or metabolic syndrome, found improvements in fasting glucose. The authors suggest the difference may reflect who was studied.

    LiverTox, which lists diabetes among the conditions spirulina is used for, states that it “has not been proven to be effective in treating any medical condition.”

    Sources: Source [1]Source [2]

  • Helps with weight loss Evidence rating: Limited

    Some people take it hoping it will help them lose weight.

    One review found a small fall in body weight, about 2% to 3%, at low certainty, and no significant change in body mass index, body fat or waist measures.

    The evidence is one graded 2025 meta-analysis, in adults with overweight or obesity. Across eight trials it found a small reduction in body weight with spirulina compared with control groups, rated low certainty. The result was no longer statistically significant when one trial was left out. It found no statistically significant difference in body mass index (very low certainty), body fat percentage (low), waist circumference (moderate) or waist-to-hip ratio (low).

    Its authors describe the weight change as roughly 2% to 3% of starting weight. That is below the 5% to 10% they cite for substantial cardiovascular risk reduction, though they add that “modest weight loss may still confer meaningful health benefits”. They also write that spirulina’s “overall impact on body composition and glycemic control appears limited”.

    LiverTox states that spirulina “has not been proven to be effective in treating any medical condition.”

    Sources: Source [1]Source [2]

  • Lowers blood pressure Evidence rating: Limited

    People with high blood pressure take it hoping it will bring their readings down.

    Four reviews, pooling overlapping trials, found lower diastolic pressure and two of them lower systolic pressure; the one review that graded its evidence rated both very low certainty.

    These reviews measured blood pressure readings, not heart attacks or strokes, and their results depend on which trials they pooled. A 2021 meta-analysis pooled five randomized trials, in 230 people with high blood pressure, type 2 diabetes, joint pain or ulcerative colitis. It found systolic pressure about 4.6 mmHg lower with spirulina than in control groups. Pooling four trials, it found diastolic pressure about 4.3 mmHg lower, with large differences between trials. The larger figure in its abstract, about 7 mmHg, comes after it removed the one trial, in ulcerative colitis, that caused those differences.

    One of the five trials in the 2021 review used a water extract enriched in phycocyanin, a spirulina pigment, for two weeks. One compared spirulina with no treatment rather than a placebo. The review found a larger fall in systolic pressure in people with high blood pressure than in those without.

    A 2025 meta-analysis of 29 trials of edible algae analyzed six of them as spirulina, in a subgroup analysis. In that subgroup it found systolic pressure about 5.3 mmHg and diastolic about 3.6 mmHg lower. Its study table shows two of them giving spirulina in a sauce or salad dressing. Neither this review nor the 2021 review rated certainty with GRADE.

    A 2025 meta-analysis in adults with overweight or obesity found lower diastolic pressure across four trials, but no statistically significant difference in systolic pressure. It rated certainty for both very low. Leaving out any one of three trials made the diastolic result non-significant. Its authors write that their results “endorse Spirulina supplementation as a clinically significant non-pharmacological strategy for blood pressure control, though high heterogeneity limits certainty”.

    A 2025 meta-analysis of spirulina and chlorella trials found a reduction in diastolic pressure but not systolic. Two of its authors are employed by the company Sea4Us. It suggests that spirulina “can be used as an adjuvant to control cardiometabolic risk factors, particularly for BP”. It also states that “the magnitude of this effect is small and of uncertain clinical significance”. Under this site’s rules, the lowest certainty the graded review gives these outcomes, very low, sets the rating.

    Sources: Source [1]Source [2]Source [3]Source [4]

  • Relieves allergic rhinitis (hay fever) symptoms Evidence rating: Limited

    People with hay fever take it hoping it will ease a runny nose, sneezing and a blocked nose.

    No cited review pooled the few small trials, and LiverTox says there have been limited studies in humans and that spirulina has not been proven effective for any medical condition.

    No cited review pooled trials of spirulina for allergic rhinitis; the cited human evidence is a few small trials. Two systematic reviews that include spirulina for allergic rhinitis, Karkos et al. (2007) and Pellow et al. (2020), exist but could not be read in full for this page. Their findings are not reported here.

    A 2024 review of spirulina and allergy describes a 2008 placebo-controlled trial. That trial reported improvements in nasal discharge, sneezing, nasal congestion and itching with spirulina. The review also describes a 2005 trial that measured immune signaling in blood cells rather than symptoms. The same review describes allergic reactions to spirulina itself (see Safety).

    A 2020 single-blind randomized trial compared spirulina with the antihistamine cetirizine for two months, with no placebo group. It enrolled people aged 8 to 58 with persistent allergic rhinitis. It reported greater improvement in runny nose, nasal blockage and loss of smell with spirulina, but no significant difference for sneezing or nasal itching.

    LiverTox lists allergic rhinitis among the conditions spirulina is used for, and states: “There have been limited studies in humans, but it has not been proven to be effective in treating any medical condition.”

    Sources: Source [1]Source [2]Source [3]

Sources

  1. Effects of spirulina supplementation alone or with exercise on cardiometabolic health in overweight and obese adults: a systematic review and meta-analysis
    Frontiers in Nutrition, 2025 · Meta-analysis · Primary source · Certainty: very low
  2. The effect of Spirulina supplementation on lipid profile: GRADE-assessed systematic review and dose-response meta-analysis of data from randomized controlled trials
    Pharmacological Research, 2023 · Meta-analysis · Primary source · Certainty: high
  3. The Role of Chlorella and Spirulina as Adjuvants of Cardiovascular Risk Factor Control: A Systematic Review and Meta-Analysis of Randomised Controlled Trials
    Nutrients, 2025 · Meta-analysis · Primary source
    Some of its authors disclose ties to industry.
  4. Spirulina
    LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, National Institute of Diabetes and Digestive and Kidney Diseases, 2019 · Health authority summary · Primary source
  5. Effect of Spirulina Supplementation on Systolic and Diastolic Blood Pressure: Systematic Review and Meta-Analysis of Randomized Controlled Trials
    Nutrients, 2021 · Meta-analysis · Primary source
  6. Edible Algae Reduce Blood Pressure in Humans: A Systematic Review and Meta-Analysis of Randomised Controlled Trials
    Journal of Human Nutrition and Dietetics, 2025 · Meta-analysis · Primary source
  7. Spirulina (Arthrospira platensis): Antiallergic Agent or Hidden Allergen? A Literature Review
    Foods, 2024 · Systematic review · Supporting source
  8. Clinical comparison of the efficacy of spirulina platensis and cetirizine for treatment of allergic rhinitis
    Acta Otorhinolaryngologica Italica, 2020 · Randomized controlled trial · Supporting source

Page history

Show all 5 changes to this page
  • — Rewritten to the content style guideline; ratings and sources unchanged.
  • — Published. All five claims, the safety section and every source passed the site's source and wording reviews over two revision rounds. Reviews that could not be read in full stay logged in docs/08-open-decisions.md.
  • — Revised after source and wording review: the phenylketonuria caution now quotes its source verbatim, the summary’s contamination wording now matches the cited review, and the allergic-rhinitis summary no longer quotes the cetirizine trial authors’ comparison with the drug.
  • — Revised after source review: added the Fu 2025 authors’ own statements on blood pressure and weight, noted two unread systematic reviews on allergic rhinitis, and dropped the “blue-green algae” alias.
  • — First drafted. Blood lipids, blood sugar, body weight and blood pressure rated limited on GRADE (very low certainty); allergic rhinitis rated limited on the LiverTox statement that human studies are limited. The safety section rests on the LiverTox entry (likelihood score D) and the harms reported by the cited reviews.