11 Intriguing Spirulina Side Effects

 by Dr. Steve Hruby
Reviewed by Dr. Steve Hruby

I am a chiropractor, father, husband, coach, entrepreneur, and motivational speaker. Feeling good about yourself is a choice: My mission is to transform lives through optimized health and overall well-being.

  Fact Checked
 by Rhealyn Tropia, RMT
Reviewed by Rhealyn Tropia, RMT

I’ve been called a Data Ninja, The Fact Checker, and a Human Search Engine. I’m an indie content curator who does research daily, and quizzes myself on the important issues of the day.

spirulina side effects

Trying to boost your health? Your quest to enhance your health through nutrients can’t go without the mention of spirulina. Spirulina is one of the oldest forms of line on earth.

To most people, it’s a superfood packed with antioxidants and high-nutrient protein levels. It has been used widely since ancient times and comes with a wide array of health benefits.

However, the plant is now commercially produced for use in the food industry and supplements.

Some health benefits include blood sugar control, weight loss, energy boost, fighting cancer, allergy relief, and many more. However, there are also side effects to taking spirulina.

Is Spirulina dangerous? Join me as I take you through the various Spirulina side effects and the correct dosages.

11 Potential Side Effects of Spirulina 

As mentioned earlier, there are various spirulina side effects consumers need to be aware of. In this section, I’ll break down the different side effects, from the typical ones to the more serious ones.

Understanding the various side effects is important to realize the danger posed by spirulina. Continue reading to learn the side effects.

1 – Typical Side Effects

Typical side effects are temporary side effects that occur after a few hours of taking spirulina. 

  • Allergic Reaction: A few persons can experience allergic reactions after taking spirulina. Some of the common allergies include swelling of the skin and rashes
  • Headache: You can also experience some headache which disappears after some time.
  • Muscle Ache: Apart from the headache, you can also experience muscle aches.
  • Sweating: You can also experience some excess sweating as spirulina action takes place in your body.
  • Sleeping Problems: Most sleep problems with spirulina do with being too sleepy. The chemicals inside produce melatonin which produces a sleep-inducing hormone.

2 – Gastrointestinal Problems

So does spirulina cause constipation? Does spirulina cause gas? These are some of the common questions people ask. Spirulina does have some gastrointestinal problems, which you need to know.

Since it’s an alga found underwater, spirulina does contain some contaminants that lead to gastric problems. Cases of indigestion and dehydration are common.

man wearing white shirt holding his stomach in pain

What about diarrhea? Does spirulina cause diarrhea? Diarrhea can also be experienced due to the contaminations. Other gastrointestinal side effects include abdominal pain and vomiting.

3 – Deficiency of Vitamin B12

There are chances of developing Vitamin B12 deficiency when taking spirulina. While some spirulina contains B12 vitamins, it’s a pseudo-B12. 

The B12 vitamin contained is the analog of the actual B12 and, therefore, can inhibit the utilization of Vitamin B12 in your body.

So technically speaking, taking spirulina can lead to vitamin B12 deficiency. Vegetarians and vegans are advised against using blue algae solely for the supplementation because of this side effect.

4 – Worsens Amino Acid Disorder

Spirulina can also worsen cases of amino acid disorders. These are disorders that affect the metabolism of amino acids in the body.

This is because of the high amino acid content in the supplements. If the body has difficulty digesting amino acids, using spirulina might worsen the case.

Most of these disorders are autosomal recessive and easily checked by analyzing the amino acid concentration in the body fluids. High amino acid concentrations are an indication of an amino acid disorder.

Simply put, your body can’t metabolize the amino acids effectively. You’re simply loading the body with more amino acids by taking spirulina. Consequently, this worsens the amino acid disorder.

5 – Possible Drug Interaction

Several cases of drug interactions have also been reported when taking spirulina. Taking spirulina can interfere with certain drugs.

Common drugs with interactions when you take spirulina are those taken for diabetes, blood thinners, and immunosuppressant drugs. However, there’s little evidence to show the supplement changes how immunosuppressants work in the body.

In the case of blood thinners, the little Vitamin K in the supplement can impact the blood thinning of certain medicines.

It’s recommended that you check the ingredient list of foods when taking certain medications.

6 – Renal Diseases

Renal diseases can also occur with excessive use of spirulina. This is why you need to follow the recommended dosages.

While metabolizing proteins, our bodies produce a significant amount of ammonia. The high amount of proteins in spirulina being metabolized leads to the production of huge amounts of ammonia.

woman with lower back pain

The ammonia is then converted into urea which is flushed through the kidneys. Flushing huge amounts of urea from the blood puts much pressure on the kidney.

This can lead to decreased efficiency of the kidney and, in some cases, renal failure. High concentrations of urea can also lead to persons developing kidney stones.

7 – Edema

There are reported cases of edema when using spirulina. The biggest cause of such cases is due to iodine in spirulina. While it’s good to have iodine in spirulina, it’s also bad since it affects the thyroid glands.

Iodine is one of the most abundant minerals in spirulina. However, when in excess, iodine and other minerals can build up in cells leading to edema. This is a condition of fluid retention in the limbs.

In some persons, such cases can lead to weight gain or loss. Can spirulina make you gain weight? Yes, when you take over 3, 500 calories of spirulina. However, that’s unlikely as a tablespoon of spirulina contains around 20 calories.

But when there are imbalances of minerals like phosphate and calcium, one can also lose weight.

8 – Pregnant and Breastfeeding Women Are at Risk

There are also side effects for pregnant and breastfeeding women. Generally, pregnant and breastfeeding are advised to avoid spirulina altogether. However, the side effects around them aren’t well-documented.

If pregnant and breastfeeding women have to take spirulina, then they have to do it under the supervision of a medical practitioner.

9 – It Has The Potential To Cause Anxiety

There’s a potential for one to be extremely anxious after taking the supplements. Since the algae grow underwater, neurotoxic chemicals are likely to be consumed.

Such chemicals can cause anxiety and other neurodegenerative disorders.

10 – Blood Clotting May Be Slowed

Lastly, spirulina can cause the blood clotting effect to slow. It contains an anticoagulant that thins the blood. This subsequently increases the time it takes for blood to clot.

When injured, clotting is necessary to prevent excessive bleeding. However, little is known about what happens to people already taking blood thinners.

So if you’re on thinners or bleeding, avoid spirulina.

11 – Toxin Contamination Is Possible

Contamination is a pretty big danger and one that happens during harvest. Since spirulina is harvested underwater, there are high chances of cytotoxin contamination. 

Toxins like microcystins can find their way into the superfood. Microcystins are bad for the liver and can lead to liver damage.

So is spirulina good for the liver? Your guess is as good as mine. With chances of contamination, spirulina isn’t good for the liver.

Contamination can also occur when commercial brands have low heavy metals, not within the safe ranges. Metals like lead, mercury, and arsenic have been traced in spirulina, posing serious questions.

What about going bad? Does spirulina go bad? This is another cause of contamination as it can go bad and even expire. Store it properly to avoid exposure to air, humidity, and light. You also need to check the expiry dates on every brand before consumption.

How To Avoid Adverse Effects

With these serious side effects, you need ways to avoid them. The safest way to avoid adverse side effects is to choose a safe spirulina supplement that follows proper dosage instructions.

First, you need to decide between spirulina powder vs tablets. Both forms of spirulina are safe and contain the same nutrient value. However, for one reason or the other, one might prefer tablets to powder forms.

With a clear choice of spirulina, go ahead and buy the correct spirulina supplements. There are several brands out there to consider.

Secondly, you need to follow recommended dosages to avoid serious side effects. While most sites say you cannot overdose spirulina, it’s essential to stick to recommended dosages. 

You also need to know when to take spirulina, morning or night. Both times are great as long as you stick to the correct doses.

Lastly, know your body condition and if you’re under any medication. It’s always important to consult your doctor if you’re under any medication.

Spirulina Dosage: How Much Should I Take?

Now that you know the various side effects of spirulina taking too much spirulina isn’t good. You need to know the right dosages and timings to take spirulina.

But first, you need to choose spirulina powder or tablets. While both have the same ingredients, dosages can be a little confusing.

The recommended dosages should range between 3-5 grams a day of spirulina powder. If you opt to take tablets, take a maximum of six 500MG tablets daily.

man with glasses having a headache and holding his temples

Is Spirulina Safe To Take Everyday?

Spirulina is safe to take daily as long as you stick to the recommended dosages. If you notice side effects, consult your doctor before you proceed.

Can Spirulina Cause Weight Gain?

Spirulina can cause weight gain and weight loss depending on how your body reacts to it. However, in most cases, it helps people lose weight.

Can Spirulina Make You Sick?

Spirulina can make you sick with mild symptoms of dizziness, headache, nausea, vomiting, abdominal pain, diarrhea, and fatigue. However, it’s usually considered safe.

Can You Get Overdose With Spirulina?

You can overdose with spirulina when you take in excess. While most sources say you can’t take an overdose, taking more than the recommended dosages can cause problems.

Can Spirulina Cause Liver Problems?

Spirulina can cause liver problems if harvested with toxic contaminants. There are a few implicated cases, but the specific role of spirulina compared to other herbal drugs hasn’t been shown.


There you go regarding the side effects of spirulina. Despite the numerous health benefits, there are a few spirulina side effects to be aware of.

Most of the side effects aren’t serious and disappear afterward. However, more long-term side effects can arise from excessive use of spirulina. That’s why you need to stick to recommended dosages.

In case of serious side effects, stop using immediately and talk to a medical practitioner. Luckily, spirulina supplements are sold in powder and tablet forms with clear dosage instructions.

Our Sunlit Organic Spirulina Tablet will you provide you the recommended dosage. Simply dissolve 12-20 tabs in your favorite drink, and you’re done!

It’s unlikely one can overdose on spirulina unknowingly. Therefore, most of these side effects are rare, with most consumers experiencing temporary side effects like headaches and sweating that disappear in hours.

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