Spirulina is a microalga (also called Arthrospira) dried and sold as a powder or tablets, and widely used as a dietary ingredient. As a supplement it has been studied mainly for cholesterol, blood pressure and other heart and metabolic markers.
Also known as: Arthrospira, Arthrospira platensis, blue-green algae.
Spirulina has no RDA or upper limit, and there is no NIH fact sheet for it. The meta-analyses below pooled trials that used different amounts and lengths, so there is no single study amount to quote.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling.
A 2023 meta-analysis of 20 trials with 1,076 people (Rahnama) found that spirulina lowered LDL cholesterol, total cholesterol and triglycerides and raised HDL compared with control groups. A 2025 meta-analysis (Shiri) found it lowered systolic blood pressure by about 4.4 mmHg and diastolic by about 2.8 mmHg, with moderate-certainty evidence, and said more high-quality trials are needed. Both pooled small trials of different products.
On safety, a US Pharmacopeia expert committee (Marles 2011) reviewed human trials, animal studies and 31 adverse event reports and gave Spirulina maxima and S. platensis a Class A safety rating, which allows quality standards for them. If you take medicine for blood pressure or cholesterol, tell your prescriber before adding spirulina.
We could not find a single published half-life or time to peak for spirulina that applies to a supplement dose, so we do not list one. It is a whole food (a dried microalga), not a single compound.
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