Spirulina: what it is, how much per day and what to look for

Short answer: Spirulina is dried Arthrospira platensis, a blue-green microalga that is biologically a cyanobacterium. You buy it as powder or tablets. There is no official recommended amount per day, so you follow the label: our spirulina tablets say 3 tablets of 500 mg twice a day, 3 grams in total. When buying, focus on purity. Spirulina is not recommended if you have PKU, an algae allergy or an autoimmune condition. If you are pregnant, breastfeeding or take medication, talk to your doctor first.

Last updated: 5 November 2026 · Written by Florian Fermin

Spirulina is one of the best-known green supplements. You see it in smoothies, bowls and as small dark green tablets. Still, many people don't know exactly what it is, how much to take and where things can go wrong.

Below I go through what spirulina is, which forms exist, how much spirulina per day the label says, what research does and doesn't show and what I look for myself when buying. Not sure whether to choose spirulina or chlorella? That is covered in our article spirulina vs chlorella: what is the difference.

What is spirulina?

Spirulina is the dried biomass of Arthrospira platensis, a blue-green microalga. Strictly speaking it is not a plant and not a true alga either, but a cyanobacterium (Verbraucherzentrale Hamburg, 2025).

On older labels you will also see the name Spirulina platensis. That is the same species. In German it is also called Spirulina, in French spiruline. Spirulina occurs naturally in warm, salty lakes. The Aztecs and peoples around Lake Chad harvested it as food centuries ago. Today spirulina is grown in ponds, harvested, dried and ground into powder or pressed into tablets.

In the EU, spirulina is an ordinary food. The European Commission's Novel Food Catalogue lists Arthrospira platensis as "not novel in food": it was already eaten in the EU before 15 May 1997, so no separate authorisation is needed (EU Novel Food Catalogue).

Spirulina powder or tablets: which form should you choose?

Choose spirulina tablets if you don't want to taste it and want to know exactly how much you take. Choose spirulina powder if you want to mix it into a smoothie or juice. Both contain only spirulina. Spirulina capsules also exist, but we don't sell them: there the spirulina sits in a shell instead of being pressed.

The amounts per tablet come from our labels. How many grams fit on a scoop of powder depends on how full you fill it. If you want to know exactly, weigh it once on a kitchen scale.

I compare the two forms in detail in spirulina tablets or powder.

How much spirulina per day?

There is no official recommended daily amount for spirulina, as there is for vitamins. So you stick to the daily dose on the packaging of your product. For our tablets that is 3 tablets, twice a day: 3 grams of spirulina in total.

The French food safety agency ANSES concluded in 2017 that spirulina at low doses, up to a few grams per day for adults, does not appear to pose a health risk, provided the product is not contaminated (ANSES, 2017). That brings us straight to the most important caveat: quality. More on that below.

• Do not go above the daily dose on the packaging.
• Take spirulina during or just after a meal, as the label says.
• Do you use several products with spirulina, for example tablets and a greens mix? Then add up how much spirulina you get in total.
• Children: our packaging states that mineral supplementation in infants and young children (0 to 3 years) should only take place under medical supervision.

The directions per product and the amounts used in research are covered in spirulina dosage.

How do you use spirulina powder?

Mix spirulina powder into a smoothie, juice or meal. It has a distinct, slightly salty taste. In a smoothie with banana, pineapple or mango you notice it least.

1. Take the scoop out of the pouch and measure 2 scoops of powder.
2. Mix it into a smoothie, juice or meal. Stir well or use a blender or shaker.
3. Do this 2 to 3 times a day, preferably during or just after a meal.
4. Close the pouch properly and store it somewhere cool, dry and dark.

Don't like the taste? Then tablets are easier. You swallow them with water and hardly taste them.

What is in spirulina?

Our spirulina contains only dried spirulina, with nothing added. These nutrition claims apply to it: Spirulina is naturally high in protein** and Spirulina is naturally a source of fibre**. This also applies: Protein contributes to the maintenance of muscle mass**.

**Authorised health claim (Regulation (EU) No 432/2012) or nutrition claim (Regulation (EC) No 1924/2006).

Vitamin B12 is a common misunderstanding. You can measure "B12" in spirulina tablets, but Japanese research showed that about 83% of it was pseudovitamin B12, a form that is not active in humans (Watanabe et al., 1999). The Dutch Nutrition Centre (Voedingscentrum) writes that in Dutch research spirulina and nori did not provide enough B12 for vegan children, and advises vegans to use a B12 supplement or fortified products (Voedingscentrum). If you eat a vegan diet, don't count on spirulina for your B12.

And iron? You often read that spirulina contains a lot of iron. Our label does not state an iron content, so we make no statement about it. If you want to know how much iron a product provides, check whether there is a nutrition table with iron on the packaging.

What does research say about spirulina?

A lot of research has been done on spirulina. Safety is the best-studied part. What spirulina does in your body exactly is much less clear.

• Safety: a committee of the United States Pharmacopeia (USP) reviewed clinical studies, animal studies, regulations and 31 adverse event reports. They gave Spirulina platensis and Spirulina maxima safety class A (Marles et al., 2011). That is an assessment of the ingredient, not a guarantee for every product.
• Traditional use: spirulina has been eaten as food for centuries, including around Lake Chad and by the Aztecs.
• Effects: the EU has not authorised any health claims for spirulina itself. That is why we make no promises about what spirulina does for you. The nutrition claims above are about its composition.

Is spirulina safe? Side effects and who should be careful

For most healthy adults, spirulina at a few grams per day appears safe, as long as the product is clean (ANSES, 2017). Still, there are groups who should check first or skip it altogether.

• Stomach and gut: some people get stomach complaints or diarrhoea when they take a lot of spirulina. This is also stated on the product page of our tablets.
• PKU (phenylketonuria): ANSES advises against spirulina for people with PKU. Like any protein source, spirulina contains the amino acid phenylalanine.
• Allergy: ANSES advises against spirulina for people prone to allergies. If you are allergic to algae, don't take it.
• Autoimmune condition: there are case reports in which symptoms got worse after supplements containing spirulina, among other things (Lee and Werth, 2004). The product page of our tablets advises against use in that case, as well as with gout and kidney stones.
• Smoking: our packaging states that the product contains beta-carotene, which is not recommended for smokers.
• Pregnant or breastfeeding: the product page of our tablets advises against use in that case. Either way, talk to your GP first.
• Medication: talk to your GP or pharmacist first, as the packaging also says.

All described side effects, and what the case reports do and do not show, are covered in spirulina side effects.

What should you look for when buying spirulina?

The most important thing with spirulina is purity. Spirulina grows in water and can become contaminated with microcystins (toxins from other blue-green algae), bacteria or metals such as lead, mercury and arsenic (ANSES, 2017). In an American analysis of 18 algae supplements, not only spirulina, some products contained more than 40 times the maximum acceptable concentration of microcystins of 1 µg per gram (Miller et al., 2020).

• Certificate of analysis (CoA): ask whether each batch has been tested for microcystins, heavy metals and microbiology.
• Traceability: ANSES recommends products with a clearly identified manufacturer, traceability and a controlled supply chain.
• Legal limits: in the EU, maximum levels apply to food supplements for lead, cadmium and mercury, among others (Regulation (EU) 2023/915).
• Ingredients: the shorter the list, the better you know what you are taking.

This is what that looks like for us. These are the results from the certificate of analysis of a batch of our spirulina tablets (produced September 2025):

You can request a CoA for our spirulina via support@getgoyu.com. Our spirulina powder and tablets are organic and contain only spirulina.

What is the difference between spirulina and chlorella?

Spirulina is a blue-green cyanobacterium from warm, salty lakes. Chlorella is a green, single-celled freshwater alga with a sturdy cell wall. They are often mentioned together and taken together too. A comparison table and an explanation of taking them together can be found in spirulina vs chlorella. What chlorella is exactly and what to look out for, you can read in chlorella: what is it and is it safe.

Do you mainly use spirulina for protein in your shake? Then our article on whey or plant-based protein is useful too.

Summary in 3 points

• Spirulina is dried Arthrospira platensis, a blue-green microalga (cyanobacterium), and is an ordinary food in the EU.
• There is no official daily amount. Our tablets say 3 tablets twice a day (3 g), our powder 2 scoops 2 to 3 times a day.
• Check for purity (a CoA with microcystins and heavy metals) and skip spirulina if you have PKU, an algae allergy or an autoimmune condition, or talk to your doctor first.

Frequently asked questions

How many spirulina tablets per day?

Our packaging says 3 tablets of 500 mg, twice a day, with water and with a meal. That is 6 tablets and 3 grams of spirulina per day in total. Do not go above that amount.

How many grams of spirulina per day are safe?

There is no official limit. ANSES writes that spirulina up to a few grams per day for adults does not appear to pose a health risk, if the product is not contaminated. So stick to the daily dose on the label.

Is spirulina a good source of vitamin B12?

No. Most of the B12 you measure in spirulina is pseudovitamin B12, which is not active in humans. If you eat a vegan diet, take a B12 supplement or fortified products, as the Dutch Nutrition Centre advises.

Can you take spirulina every day?

Yes, the directions on the packaging are meant per day. Stick to that amount, choose a product with a CoA and talk to your doctor if you are pregnant, take medication or have a medical condition.

Spirulina capsules or tablets: what is the difference?

Both contain spirulina. Tablets are pressed powder, capsules have a shell. Look mainly at what else is on the ingredient list besides spirulina and how many milligrams each one contains.

Sources

1. European Commission. Novel Food Catalogue, entry Arthrospira platensis (POL-NF-00152): not novel in food. food.ec.europa.eu
2. ANSES. Compléments alimentaires à base de spiruline: privilégier les circuits d'approvisionnement les mieux contrôlés (opinion 2014-SA-0096), 30 November 2017. anses.fr
3. Marles RJ, Barrett ML, Barnes J, et al. United States Pharmacopeia safety evaluation of spirulina. Crit Rev Food Sci Nutr. 2011;51(7):593-604. doi:10.1080/10408391003721719
4. Watanabe F, Katsura H, Takenaka S, et al. Pseudovitamin B12 is the predominant cobamide of an algal health food, spirulina tablets. J Agric Food Chem. 1999;47(11):4736-4741. doi:10.1021/jf990541b
5. Voedingscentrum (Dutch Nutrition Centre). Zeewieren en algen. voedingscentrum.nl
6. Miller TR, Xiong A, Deeds JR, et al. Microcystin toxins at potentially hazardous levels in algal dietary supplements. J Agric Food Chem. 2020;68(30):8016-8025. doi:10.1021/acs.jafc.0c02024
7. Lee AN, Werth VP. Arch Dermatol. 2004;140(6):723-727. doi:10.1001/archderm.140.6.723
8. Verbraucherzentrale Hamburg. Algen essen: Auf den Jodgehalt achten, 4 February 2025. vzhh.de
9. Commission Regulation (EU) 2023/915 on maximum levels for certain contaminants in food. eur-lex.europa.eu
10. Packaging texts and product pages of Spirulina Tablets, Spirulina Powder and Spirulina Chlorella Tablets, and certificate of analysis batch SRORGLXZ250902P, consulted 5 November 2026.

You can find all our spirulina, on its own or combined with chlorella, on the page buy spirulina. Looking for chlorella or sea moss too? You can find all our algae together in our algae supplements.

This article is for information only and is not medical advice. Food supplements are not a substitute for a varied and balanced diet and a healthy lifestyle. If in doubt, pregnant or taking medication, talk to your GP or pharmacist.