Spirulina side effects: what can you notice?

Short answer: The side effect mentioned most often is stomach and gut trouble, such as diarrhoea, especially when you take a lot of spirulina. Rarer are allergic reactions and individual reports of liver and muscle problems; in some reports, contamination of the product played a role. At the dose on the label, spirulina appears to be safe for healthy adults, but if you have PKU, an algae allergy or an autoimmune condition, are pregnant or take medication, talk to your doctor first.

Last updated: 5 November 2026 · Written by Florian Fermin

Spirulina has a healthy image, but a green powder or tablet can still cause complaints. We sell spirulina, and that is exactly why we set out honestly what is known about spirulina side effects here: how often they occur, what the cause can be and when to stop or see your GP.

What spirulina is and how much to take is covered in our article what is spirulina.

What side effects can spirulina cause?

Most reports are about the stomach and gut. In addition, there are allergic reactions and a small number of case reports about the liver, muscles and autoimmune complaints. In reports about spirulina, the French food safety agency ANSES mentions "digestive disorders, allergy, and muscle or liver problems", and writes that the amounts taken were usually not known precisely. According to ANSES, the available studies are too small to detect rare side effects (ANSES, 2017).

Can spirulina cause stomach and gut complaints?

Yes. The product page of our spirulina tablets states: "Some people may experience stomach problems and diarrhoea when taking a lot of spirulina." ANSES also mentions digestive complaints among the reports it received.

How often this happens, we don't know: the studies are too small for that. What you can do yourself:

1. Take spirulina during or just after a meal, as the label says.
2. Start lower than the full daily dose and build up. Taking less than the label says is always fine.
3. Split the daily dose over 2 moments instead of taking it all at once.
4. If the complaints persist, stop and talk to your GP.

How much to take per day according to the label is explained in spirulina dosage.

Can you be allergic to spirulina?

Yes, although it seems rare. In a French case report, a teenager had a severe allergic reaction (anaphylaxis) after spirulina. The researchers identified phycocyanin, the blue pigment in spirulina, as the protein he reacted to (Petrus et al., 2010).

ANSES advises against spirulina if you are prone to allergies, and the product page of our tablets advises against it if you are allergic to algae. Do you get itching, a rash, swelling of the face, lips or throat, or difficulty breathing after spirulina? Stop immediately, and if there is swelling or shortness of breath, call 112.

Is spirulina bad for your liver or muscles?

With normal use of a clean product, there is little evidence of that. There are, however, individual case reports:

• Liver: a Japanese case report describes liver problems in a man who used spirulina (Iwasa et al., 2002). ANSES also mentions liver problems among the reports.
• Muscles: a Greek case report describes acute rhabdomyolysis, a severe form of muscle breakdown, after taking spirulina as a supplement (Mazokopakis et al., 2008).

These concern only a few people. Such a report shows that something can happen, not how often it happens, and it is often not certain whether spirulina itself or something else was the cause. A committee of the United States Pharmacopeia reviewed clinical studies, animal studies and 31 adverse event reports, and still gave spirulina safety class A (Marles et al., 2011). That is a judgement about the ingredient, not a guarantee for every product.

If you develop unexplained complaints after starting spirulina, such as persistent tiredness, yellow eyes or skin, or muscle pain and weakness, stop and see your GP. Take the packaging with you.

Are side effects caused by spirulina or by contamination?

Sometimes by contamination. Spirulina grows in water and can become contaminated during cultivation with microcystins (toxins from other blue-green algae), bacteria or metals such as lead, mercury and arsenic (ANSES, 2017). Microcystins can put a strain on the liver. In an American analysis of 18 algae supplements, some products contained more than 40 times the maximum acceptable concentration of 1 µg per gram (Miller et al., 2020). Not all products tested were spirulina, but it shows why purity matters.

That is why these are the most important checks when buying:

• a certificate of analysis (CoA) per batch, tested for microcystins, heavy metals and microbiology;
• a clearly identified manufacturer and traceable origin, as ANSES advises;
• a short ingredients list.

What this looks like for our spirulina, with the results of a real certificate of analysis, is shown in our in-depth article about spirulina. You can request a CoA via support@getgoyu.com.

Who is spirulina not recommended for?

The product page of our tablets and ANSES advise against spirulina in case of:

• PKU (phenylketonuria): like any protein source, spirulina contains the amino acid phenylalanine.
• An algae allergy or a tendency to allergies.
• An autoimmune condition: in case reports, complaints got worse after supplements containing spirulina, among other ingredients (Lee and Werth, 2004).
• Gout and kidney stones.
• Pregnancy and breastfeeding.

In addition, our spirulina powder and the Spirulina Chlorella Tablets state that they contain beta-carotene, which is not recommended for smokers. And according to our packaging, mineral supplementation in children up to 3 years should only take place under medical supervision.

Can you combine spirulina with medication?

Talk to your GP or pharmacist first. The product page of our tablets states that spirulina can interact with other medication, and our packaging says to consult your doctor first if you take medication. Exactly which medicines is poorly studied. That is precisely why it is wise to let your pharmacist check.

What should you do if you get complaints?

1. Stop or take less. With mild stomach or gut complaints, you can first take less or take spirulina with a meal.
2. Swelling of the face or throat, or short of breath? Call 112 immediately.
3. Persistent or severe complaints? See your GP and take the packaging with you, so it is clear exactly what you used.
4. Let us know. Email the batch number and your complaints to support@getgoyu.com, so we can check the batch.

Torn between spirulina and chlorella, for example because spirulina does not agree with you? Then read spirulina vs chlorella.

Summary in 3 points

• The most frequently mentioned side effect of spirulina is stomach and gut trouble, especially with larger amounts. Allergic reactions and liver or muscle problems are rare and mainly known from individual case reports.
• Contamination with algal toxins, bacteria or heavy metals is an important cause of problems. Choose a product with a certificate of analysis and a clear origin.
• Do not use spirulina if you have PKU, an algae allergy, an autoimmune condition, gout or kidney stones, or during pregnancy or breastfeeding, and talk to a doctor first if you take medication.

Frequently asked questions

Can spirulina cause diarrhoea?

Yes. The product page of our tablets states that some people get stomach problems and diarrhoea when they take a lot of spirulina. Take it with a meal, start lower and stop if the complaints persist.

Is spirulina bad for your liver?

There are individual case reports of liver problems after spirulina, and contamination with microcystins can put a strain on the liver. With a clean product at the dose on the label, there is little evidence of this. Choose a product with a certificate of analysis and talk to your doctor if you have a liver condition.

How quickly do you notice side effects of spirulina?

That has not been studied well. You usually notice stomach and gut complaints in the days after you start or increase the amount. An allergic reaction can occur soon after taking it. If you get complaints, stop and talk to your GP.

Can you use spirulina when you are pregnant?

The product page of our tablets advises against use during pregnancy and breastfeeding. Always talk to your midwife or GP before you start using a supplement.

Is spirulina dangerous for people with an autoimmune condition?

There are case reports in which complaints got worse after supplements containing spirulina, among other ingredients. That is why the product page of our tablets advises against use if you have an autoimmune condition.

Sources

1. ANSES. Compléments alimentaires à base de spiruline: privilégier les circuits d'approvisionnement les mieux contrôlés (opinion 2014-SA-0096), 30 November 2017. anses.fr
2. Marles RJ, Barrett ML, Barnes J, et al. Crit Rev Food Sci Nutr. 2011;51(7):593-604. doi:10.1080/10408391003721719 (safety evaluation, 31 reports)
3. Petrus M, Culerrier R, Campistron M, Barre A, Rougé P. Allergy. 2010;65(7):924-925. doi:10.1111/j.1398-9995.2009.02257.x (case report, 1 person)
4. Iwasa M, Yamamoto M, Tanaka Y, Kaito M, Adachi Y. Am J Gastroenterol. 2002;97(12):3212-3213. doi:10.1111/j.1572-0241.2002.07145.x (case report, 1 person)
5. Mazokopakis EE, Karefilakis CM, Tsartsalis AN, Milkas AN, Ganotakis ES. Phytomedicine. 2008;15(6-7):525-527. doi:10.1016/j.phymed.2008.03.003 (case report, 1 person)
6. Lee AN, Werth VP. Arch Dermatol. 2004;140(6):723-727. doi:10.1001/archderm.140.6.723 (case reports, 3 people)
7. Miller TR, Xiong A, Deeds JR, et al. J Agric Food Chem. 2020;68(30):8016-8025. doi:10.1021/acs.jafc.0c02024 (analysis of 18 supplements)
8. Packaging texts and product pages of Spirulina Tablets, Spirulina Powder and Spirulina Chlorella Tablets, consulted 5 November 2026.

You can find our spirulina, on its own or combined with chlorella, on the page buy spirulina.

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.