Spirulina Dosage: How Much Per Day (1-8g, No "Active %")
Most spirulina labels say about 3 g a day: one scoop of powder or 6 tablets of 500 mg. Studies used 1 to 8 g a day. Spirulina is a whole food, not an extract, so there is no “active %” to check. The dose is just grams.
Based on published research, not medical advice. Skip spirulina if you have an autoimmune disease or PKU. Pregnant, breastfeeding or take medicines? Ask your doctor first.
Ready to buy:
Zazzee Organic Spirulina Powder$0.12 per 3 g. 3.3 g a scoop, the lowest cost per 3 g we found, and the brand says a lab tests for algae toxins and heavy metals. Why it is our pick.
Costs are brand prices, checked October 18, 2026.
Which spirulina is right for you?
Powder is the cheapest way to get 3 g. If you would rather swallow tablets, count them.
Taking 500 mg tablets? You need six.
Check the tablet size on the label. At 500 mg a tablet, it takes 6 to make a 3 g serving and 2 to make 1 g. Nutrex Hawaii tablets list 6 as a serving. They cost 4.1 times our powder pick per 3 g.
Nutrex Hawaii Pure Hawaiian Spirulina Tablets
$0.49 for 6 tablets (3 g)
Want fewer tablets? Pick 1 g tablets.
NOW makes 1 g tablets, so 3 tablets make a 3 g serving. They cost more per 3 g than the 500 mg tablets above at each brand’s own price, but you swallow half as many.
NOW Organic Spirulina Tablets
$0.55 for 3 tablets (3 g)
New to spirulina? Start small.
Starting with 1 to 3 g a day and working up is common. A level teaspoon of powder is about 3 g. The calculator below adds up the grams if you use tablets or a different scoop.
Have an autoimmune disease? Skip it.
Spirulina stimulates the immune system, and doctors have reported flares of autoimmune disease in people taking it (de Carvalho 2025). That is a reason to avoid it at any dose.
How much spirulina per day
The studies dosed grams of dried spirulina: 1 to 8 g a day across trials on cholesterol, blood pressure and blood sugar (Karkos 2011). A trial in people with hay fever used 2 g a day (Cingi 2008). No dose has a clear effect yet, so a label’s 3 g is a reasonable middle.
How to take it
- Mix powder into a smoothie or juice. It tastes strong on its own.
- Take tablets with water. Split them across the day if 6 at once is too many.
- Take it any time of day. No study shows one time works better.
Work out your daily grams
Enter the numbers from any spirulina label. You will see the grams you take a day and, if you add the price, the cost per 3 g.
Questions people ask
How many spirulina tablets make 3 g?
It depends on the tablet size, so check the label. It takes 6 tablets of 500 mg, or 3 tablets of 1 g. Powder is simpler: a level teaspoon is about 3 g.
Can you take too much?
No upper limit has been set for spirulina. Studies went up to 8 g a day, and we found none showing that more works better. More spirulina also means more of whatever a poorly made batch carries, such as heavy metals. That is why a stated test matters more than a bigger dose.
Related guides
- Best spirulina: every product we scored, ranked by testing and cost per 3 g
- Is your spirulina clean?: toxins, heavy metals and which brands state their tests
- Spirulina guide: what it is and what the research covers
Sources
- Karkos PD, et al. “Spirulina in clinical practice: evidence-based human applications.” Evid Based Complement Alternat Med. 2011. PubMed 18955364
- Cingi C, et al. “The effects of spirulina on allergic rhinitis.” Eur Arch Otorhinolaryngol. 2008. PubMed 18343939
- de Carvalho JF, et al. “Spirulina ingestion and autoimmune disease onset or flare.” Letter. Adv Rheumatol. 2025. PubMed 40087772
- Serving sizes and prices from each brand’s own label and store.