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Limited evidenceHerbs & superfoods

Spirulina

Also called: Blue-green algae

A protein-rich algae with iron and antioxidants. Only buy tested batches.

Typical amount
1–3 g a day
Best time
Morning, with breakfast
Food
With food
Typical course
8 weeks, then review
Is it right for me?

Where to buy

3 products

What is spirulina?

Spirulina is a blue-green algae grown in fresh water. It contains protein, iron, B vitamins (though its B12 isn't usable by the body) and antioxidant pigments. Poorly grown spirulina can be contaminated with toxins or metals, so testing matters.

Forms. Tablets, capsules and powder.

What it may help with

Evidence grade

Strong: several good human trials. Moderate: some trials, mixed results. Limited: small or early studies. Traditional: long use, little trial evidence.

Safety and interactions

Side effects
Stomach upset. Avoid with autoimmune disease, PKU, or on immunosuppressants. Contaminated products can harm the liver.
Who should be careful
Buy tested batches only; autoimmune disease, PKU, immunosuppressants: avoid
Medicines
Avoid if you take steroids or immunosuppressants. Ask your doctor first if you take pregnancy or breastfeeding.
Stop and call a doctor if
Rash, stomach pain, dark urine

Food sources

Not part of typical diets; it is a supplement food.

Common questions

Does spirulina give me B12?

No. It contains a B12-like compound the body can't use.

How much should I take?

1–3 g a day with breakfast, or as the label says.

Is it good for vegans?

It adds protein and iron, but vegans still need a real B12 supplement.

For information only, not medical advice. Prices and links are checked by hand and can change; we may earn a small commission on some links. This plan is based on your answers and is not a medical diagnosis. It does not replace advice from your doctor. If you take medicines or have a health condition, check with your doctor before starting any supplement.