Spirulina
Spirulina in powder, tablets and capsules. We explain how the forms differ, why we look for tested, cultivated algae rather than wild-harvested, and what a daily dose of a few grams realistically does for you.Read more →
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How to choose a spirulina supplement
Spirulina is a blue-green algae grown in warm, alkaline water. The type used in supplements is Arthrospira platensis. Dried spirulina is roughly 55 to 70 percent protein and holds two natural pigments: green chlorophyll and blue phycocyanin. Together they give the powder its dark colour and its strong, pond-like smell. Nothing is extracted or concentrated, so what you buy is the whole dried algae. Shoppers often compare it with chlorella, a green freshwater algae with a different nutrient profile and a tougher cell wall.
The forms differ in dosing and taste, not in the algae
Powder, tablets and capsules all start as the same dried biomass. Tablets are pressed powder. Capsules are the same powder in a shell. What changes is how much you get per serving and how much you taste. One level teaspoon of powder holds about as much as six 500 mg tablets, which is why tablet packs run into the hundreds. Powder gives you the most control per gram and stirs into smoothies. Tablets and capsules hide the taste and travel better. For anyone following a plant-based diet, powder is usually the cheaper way to take a larger daily amount.
Where it grows matters more than the label design
Algae take up what surrounds them. Spirulina from open, uncontrolled water can pick up heavy metals, or toxins from other cyanobacteria growing alongside it. That makes cultivation and batch testing more important here than for most plant ingredients. Three things are worth checking on a pack: a named growing region, the stated species, and testing for heavy metals and microcystins. Organic certification tells you how the algae were grown. It is not the same thing as a contaminant test.
How we choose the spirulina we stock
We list spirulina from controlled cultivation only, never wild-harvested algae, and we ask brands for batch results on heavy metals and microcystins before a product goes live. We prefer plain pressed tablets and pure powder over green blends, because you can then see exactly how many grams you take. A combination only earns a place when it makes sense, spirulina with chlorella being the obvious one. We buy directly from the brands, our compliance team checks every label, and independent labs spot-check batches. You can read how we select brands and products.
Who it suits, and what a daily dose realistically does
Spirulina is a nutrient-dense food, not a quick fix. It suits people who eat little or no animal protein, anyone who wants a compact source of plant protein and iron, and people who simply want to add greens without cooking. Where a serving delivers a significant amount of iron, that iron contributes to the reduction of tiredness and fatigue and to the normal function of the immune system. The amount per serving differs a lot per product, so read the label rather than the front of the pack.
- Powder: largest amounts, lowest cost per gram, noticeable taste
- Tablets: pressed powder, easy to count, high tablet numbers per day
- Capsules: no taste, smallest amount per unit
Most people take 2 to 5 grams a day and judge the result after three to four weeks of consistent use. Start with a small amount if your stomach is sensitive, then build up over a week or two. You will find spirulina alongside the rest of our herbal and plant range.
Frequently asked questions
What is spirulina?
Spirulina is a blue-green algae, a cyanobacterium, grown in warm alkaline water. Supplements use the species Arthrospira platensis. The algae are harvested, dried and either packed as powder or pressed into tablets. Dried spirulina is roughly 55 to 70 percent protein and contains iron, B vitamins and two pigments: green chlorophyll and blue phycocyanin. Because it is whole dried food rather than an extract, the nutrient amounts depend on where and how it was grown.
What do people take spirulina for?
Most buyers use it as a compact plant food rather than for one single effect. It is popular with people eating little or no animal protein, because a few grams add protein, iron and B vitamins to the day. Where a serving provides a significant amount of iron, that iron contributes to the reduction of tiredness and fatigue and to the normal function of the immune system. Amounts differ per product, so check the label before assuming a serving is meaningful.
Which form should I choose: powder, tablets or capsules?
All three contain the same dried algae, so choose on taste, cost and how easily you keep it up.
| Form | Taste | Dose control | Suits |
|---|---|---|---|
| Powder | Strong, pond-like | Highest | Smoothies, larger daily amounts |
| Tablets | Neutral | Good, by count | Fixed daily routine, travel |
| Capsules | None | Good, smallest per unit | Sensitive palates, low doses |
Powder is normally the cheapest per gram. Tablets cost more but remove the taste question entirely.
How much spirulina should I take a day, and when?
Common daily amounts sit between 2 and 5 grams, which is around one to two level teaspoons of powder or six to ten 500 mg tablets. Manufacturer instructions differ, so follow the pack. Timing is flexible: spirulina is a food, not a stimulant, and many people take it with breakfast simply because it is easier to remember. If you are new to it, start at about 1 gram for a week. This lowers the chance of mild bloating while your digestion adjusts.
Is spirulina a reliable source of vitamin B12?
No, and this is worth knowing before you buy. Analyses of algae supplements show that the B12 in spirulina is mostly pseudo-vitamin B12, a look-alike molecule the human body cannot use. It can also show up in older lab methods as if it were the real thing. If you eat a plant-based diet, use a proper vitamin B12 supplement or fortified foods, and treat spirulina as a source of protein and iron instead.
How much of my daily iron does spirulina actually cover?
That depends on the product, but it helps to know the UK reference amounts first.
| Group | Iron a day |
|---|---|
| Men 19 and over | 8.7 mg |
| Women 19 to 49 | 14.8 mg |
| Women 50 and over | 8.7 mg |
Iron from plants is absorbed less easily than iron from meat, so spirulina is a useful contribution rather than a replacement for an iron supplement if you have a shortfall.
Source: NHSWhat is the difference between spirulina and chlorella?
Spirulina is a blue-green algae from warm alkaline water. Chlorella is a green freshwater algae with a hard cell wall, which is why good chlorella is sold as broken cell wall. Spirulina is higher in protein and contains phycocyanin. Chlorella is higher in chlorophyll and, unlike spirulina, some products do contain usable vitamin B12. Many people take both. If you want one, choose spirulina for protein and iron, chlorella for chlorophyll.
Is spirulina safe, and who should avoid it?
For most adults, spirulina from controlled cultivation and tested batches is well tolerated, and mild digestive changes in the first days are the usual complaint. The real risk is quality: algae can carry heavy metals, bacteria or cyanotoxins such as microcystins if grown or handled poorly. The French food safety agency ANSES advises against spirulina supplements for people with phenylketonuria or an allergic predisposition. If you are pregnant, breastfeeding or on medication, ask your GP or pharmacist first.
