Spirulina Powder: What It Does, Dose and Heavy Metal Risk

Short answer: spirulina powder is a dried, cultivated cyanobacterium (often called blue-green algae). It is around 60% protein by dry weight and carries iron, beta-carotene and the blue pigment phycocyanin. At the 1 to 8 g a day people usually take, it is a modest nutrient contribution, not a meal or a medicine. Its vitamin B12 is mostly an inactive form, and the main thing to check before buying is testing for heavy metals and algal toxins.

Last updated: October 2026.

Key takeaways

• Spirulina is protein-dense, but a 3 g serving gives only about 2 g of protein.
• Most of the B12 measured in spirulina is pseudovitamin B12, which the human body cannot use.
• It grows in open ponds or tanks, so what is in the water can end up in the powder. Per-batch testing matters.
• Blue spirulina is an extract of the pigment phycocyanin, not the whole organism.

What spirulina powder is

Spirulina is the common name for Arthrospira platensis and related species, a cyanobacterium grown in alkaline water in ponds or tanks, harvested, washed and dried into a dark blue-green powder. India grows a large share of its own, much of it in the south.

It is often listed next to chlorella, but they are different organisms. Chlorella is a true green alga with a tough cell wall that has to be cracked for digestion. Spirulina has a soft wall and needs no cracking. Broken-cell chlorella covers the other one.

What is in it

Component	What the figure means
Protein	Around 55 to 65% of dry weight. A 3 g serving is about 2 g of protein, so it is not a protein supplement at normal doses.
Iron	A meaningful amount per gram for a plant source, though values vary by grower and water.
Beta-carotene	A precursor the body converts to vitamin A.
Phycocyanin	The blue pigment, and the compound much of the laboratory research has focused on.
Vitamin B12	Measured on many labels, but mostly pseudovitamin B12, which is inactive in humans.

What spirulina does, and what the research covers

Most spirulina research is small. Trials have looked at blood lipids, blood glucose and markers of inflammation, often in people with existing conditions, at doses from about 1 to 10 g a day. Results lean positive but the studies are short and varied, and none of it makes spirulina a treatment. In India it is sold as a food supplement, regulated as food, and cannot claim to treat or prevent anything.

The honest description is a nutrient-dense ingredient that adds protein, iron and pigments in small amounts. That is a reasonable reason to include it in a greens blend. It is not a reason to expect a noticeable effect from one scoop.

The B12 problem

Spirulina is often sold to vegetarians as a B12 source. It is not a reliable one. A study of spirulina tablets found that most of the B12-like compound present was pseudovitamin B12, a form the human body cannot use. Standard lab tests can count it as B12, which is why a label can show a figure that does not help you. If you are vegetarian and worried about B12, a tested B12 supplement or fortified food is the dependable route. Made for the Indian body explains why B12 shortfall is common here.

Heavy metals and algal toxins

Spirulina takes up what is in the water it grows in. Product surveys have found most commercial spirulina within heavy metal limits, but with real variation between brands, and some samples high in lead or cadmium. Wild-harvested blue-green algae of other species can carry microcystins, liver toxins made by some cyanobacteria. Cultivated spirulina grown in controlled conditions is a lower risk, but only testing tells you about the batch in your hand.

What to ask for:

• A certificate of analysis for your batch, covering lead, arsenic, cadmium and mercury. How to read a COA.
• A microcystin test, or a clear statement that the material is cultivated Arthrospira rather than wild-harvested algae.
• Microbial limits, because a moist, protein-rich powder can grow bacteria if handled badly.

The wider picture is in heavy metals in greens powders.

How much people take, and how

Studies commonly use 1 to 8 g a day. As a food, a level teaspoon is roughly 3 g. Stir it into water, juice, a smoothie or curd. It tastes strongly of the sea, which is why most people take it inside a blend rather than on its own. Start with a smaller amount if you are new to it.

Who should check with a doctor first

• People with phenylketonuria, because spirulina contains phenylalanine.
• People with autoimmune conditions or on immune-suppressing medicine.
• Anyone pregnant or breastfeeding, or giving it to a child.

Spirulina in a greens blend

In a blend, spirulina is one of several plant bases alongside grass juice powders and chlorella. What matters is that it is named on its own line, not hidden inside a proprietary blend, and that the batch is tested. How to choose a greens powder in India covers the full set of checks.

Where SWATVA stands

Daily Greens includes spirulina powder, named on its own line in the ingredient ledger. Every batch is tested for ingredient identity, heavy metals and microbial limits at an NABL-accredited laboratory before release, and the report is published against the batch code. We do not count spirulina as a B12 source; the vitamin-mineral premix carries B12 for that reason.

The first run is 55 pouches. Pre-ordering takes four minutes and nothing is charged.

Sources

• Watanabe et al., 1999. Pseudovitamin B12 is the predominant cobamide of an algal health food, spirulina tablets. Journal of Agricultural and Food Chemistry
• USDA FoodData Central, Seaweed, spirulina, dried: composition per 100 g.

Common questions

Is spirulina safe to take daily?

Studies commonly use 1 to 8 g a day and report it as generally well tolerated. The bigger risk is quality, so choose a product with a per-batch test for heavy metals and algal toxins. People with phenylketonuria or an autoimmune condition, and anyone on immune-suppressing medicine, should ask a doctor first.

Does spirulina contain vitamin B12?

Mostly not in a form your body can use. Most of the B12 measured in spirulina is pseudovitamin B12, which is inactive in humans, so vegetarians should not rely on it.

What nutrients are in spirulina?

It is around 60% protein by dry weight and carries iron, beta-carotene and the blue pigment phycocyanin. At a typical 3 g serving that is only about 2 g of protein.

What is the difference between blue and green spirulina?

Green spirulina is the whole dried organism. Blue spirulina is an extract of phycocyanin, its blue pigment, used mainly for colour. They are different products.