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How do I Use Spirulina for Weight Loss?

By Deborah Woehr
Updated Mar 03, 2024
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Those who want to use spirulina for weight loss typically consume around 500 milligrams per day, generally before meals. People have their choice between different forms of the supplement, taking it alone or mixed in foods, but all forms are rich in nutrients, especially protein, that reportedly curb appetite and boost metabolism. Researchers have yet to prove that it is an effective weight loss tool or to standardize dosing, and it can interact with certain medical conditions and prescriptions, so anyone who wants to take it should get advice from a medical professional first.

About the Supplement

Spirulina is a type of consumable microalgae or cyanobacteria. Bluish green in color, it usually grows where it is warm, but people successfully cultivate it in labs around the world, making it available in a variety of climates. Most of what people eat is of the Arthrospira platensis and Arthrospira maxima families. Although it didn’t really come onto the market as a dietary supplement until the 1970s, people have consumed it for hundreds of years, usually harvesting it and drying it into cakes. The Aztecs, a large empire of Mesoamerican people who lived around what is now Mexico City, reportedly harvested it as a food source as early as the 15th century.

Available Forms

To make spirulina easier to consume, manufacturers put it into several forms, including the pill form that is common with many other vitamins and supplements. The flake version is good for sprinkling onto foods, such as salads, and some individuals prefer the powder type because it is easily mixed into juices and other drinks such as smoothies. These latter kinds also are good options for people who have trouble swallowing tablets, but they don’t provide the convenience of being premeasured. A person can pick whichever one works best given his dietary habits.


The dose most companies promote for an adult is 500 milligrams per day, which works out to about four to six tablets, but some sources bump the dose up to as much as eight pills. The amount to take isn’t standardized, however, in part because research is still ongoing regarding the benefits and drawbacks the algae has. In some regions, its status as a supplement means that major food regulatory agencies don’t monitor or control it, such as is the case with in the United States Food and Drug Administration (FDA). Most medical professionals recommend getting consultation first before adding it to the diet of anyone under age 18.

When to Take It

The ideal time to take a spirulina for weight loss generally is before a meal, with most recommendations hitting a window of 15 minutes to an hour before eating. The idea is that consuming the supplement during this period will suppress appetite, making it a little physically easier to keep portions under control. Many people take it during a meal however, adding it to their main dishes or drinks. In some cases, such as if a person is simply trying to get a nutrient boost rather than to limit how much he ingests, it’s typically better to take the algae after eating. Some people have reported some nausea if they try to use it following regular eating.

Why It Might Work

This supplement is a rich source of multiple nutrients, including riboflavin, thiamine folic acid, Vitamins A, C, D and E, zinc, iron, calcium, potassium and amino acids such as gama linolenic acid. All these substances play a part in maintaining good physical function and carrying out metabolic processes, so they are critical to being able to perform exercise and burn a maximum amount of calories. The real claim to fame for spirulina for weight loss, however, is that it is around 60% protein, which can make the number on the scale go down for multiple reasons.

Protein slows down how fast food moves through the digestive system and stabilizes blood sugar levels, which, for most people, means feeling full longer, as well as not reaching for additional snacks or eating huge amounts at subsequent meals. It also requires more energy to break down and use compared to fats and carbohydrates. Additionally, the body uses protein to build muscle tissue, which ends up using more calories to sustain over time and revving up metabolism — put another way, the leaner someone is, the more energy they usually burn. Spirulina is one option people have to get some of the dietary protein necessary to get these benefits.


No research studies have shown that using spirulina for weight loss is effective. It isn’t clear whether it is the algae or other lifestyle choices that frequently accompany supplement use, such as eating low-calorie foods and exercising, that result in slimming down. The University of Maryland Medical Center asserts that a person would need to consume quite a bit of the algae for it to do much good, and that someone can get similar amounts of protein in smaller servings of other foods, such as meat or nuts. The general consensus from medical professionals is that, although adding it to a diet probably won’t hurt, it’s an expensive route to go, as it’s about 30 times pricier per gram than the majority of other protein options.


This substance has the potential to stimulate the immune system. For many people, this is an excellent benefit, but individuals who have particular autoimmune conditions, such as arthritis and multiple sclerosis, generally should not take spirulina for weight loss, because it can aggravate these diseases. It also can interact with a number of medications prescribed for immune system suppression, such as mycophenolate, mexotrexate and cyclosporine. People with phenylketonuria, a condition that makes it hard for someone to handle phenylalanine, an amino acid the algae and other foods contain, also should avoid this product. The supplement contains high levels of Vitamin K, so it isn’t good for people who are on anticoagulant medication.

Sometimes, spirulina contains contaminants called microcystins, which, if consumed, can cause digestive issues and, potentially, cancer. Another worry is that metals occasionally find their way into the algae cultures, with mercury being of particularly high concern. Choosing a reputable manufacturer or vendor can improve the quality of the supplement and reduce the risk of these issues.

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Discussion Comments

By anon973830 — On Oct 14, 2014

I have used spirulina since the early 1980s. What a godsend! I still believe it is the original and the best superfood.

If you're menstruating, start taking a good dose a week before it starts, and your cramps and especially mood swings will not even appear. This is from my personal experience and that of everyone I recommended it to. Take it during the period as well, but if you don't want to take it the whole month, you can then stop for two weeks before again starting the week before your period begins.

It gets rid of food cravings completely, but again, it needs a week to click in, because it's a food, not a drug, so you have to give it a week to fill up the nutritional cracks.

It definitely cuts appetite, because again, it's nourishing you. Getting out of the habit and enjoyment of eating a lot / fattening stuff is a different thing.

I'm a tall person (1.8m/5'11), and I take between 12 and 24 of the 500mg tablets a day if I have a specific purpose in mind. It used to be 12 a day for menstruation nourishment (now in menopause). I'm currently taking double that for appetite suppression and deep nourishment during slimming. There have been zero side effects for me.

What this article is saying about 500mg per day (which is one tablet) is bizarre to me. You won't notice any difference with such a low dose. If one is nervous about trying something new, of course start out as low as you wish, but then manage your expectations while you build the dose, because it will probably take much longer than a week to begin to feel the benefits.

By anon347351 — On Sep 06, 2013

I bought this supplement for the same reason as any other: for health and well being, especially because it's not man made, but growing and making its own formula of so vitamins and chlorophyll.

It helped me feel full of energy, and overall, great. As a side effect I lost some weight (I'm tall, wearing S size, jeans M, so it wasn't my goal) which was pleasant, because after others mentioned that I looked thinner, I found something I didn't know when buying it: Spirulina is a so-called 'fat burner.' It burns fats that normal metabolism can't reach or something like that. That's no surprise, because it's a huge amount of proteins (like if you ate chicken breasts all month). So I lost about 3kg, which is not much, so how could others mention that? It's because it was 5 cm from the hips.

By andee — On Jul 30, 2012

Maybe I wasn't consistent enough with taking spirulina, but I didn't notice a difference when I took it to lose weight. This was a weight loss tip I read in a magazine, and thought it sounded like a natural thing to try.

I am the type of person who doesn't have a lot of patience, and if I don't see quick results, I get discouraged. Even though I was probably receiving other benefits from taking the spirulina, I don't think I lost any weight with it.

It sounds like it is something that has worked for a lot of people. It might have worked for me if I had been more patient. Between not giving it enough time, and skipping days here and there, I probably didn't give it a good chance to work the way it's supposed to.

By julies — On Jul 29, 2012

I buy my spirulina from a very reputable company that I trust, and I see it as an investment in my health. I am not looking for a quick weight loss program because I know how easy it is to put this weight back on.

I figure the slower I can lose the weight, the better. Even if I just lost a pound a week, after a year, that would be around 50 pounds.

The first time I bought spirulina I bought the powder because it was cheaper. I had a hard time getting this down and didn't care for the taste at all. Even when I mixed it in with a smoothie, it turned everything a green color.

Since then I have bought the tablets. They cost more, but at least I don't have any trouble taking them this way. After 3 months, I have lost 9 pounds, and have kept it off, so I think it is working.

By bagley79 — On Jul 28, 2012

When taking spirulina for weight loss is there a certain recommended amount? Would you take a larger amount if you wanted to lose weight than if you were just using it for other benefits?

I know that drinking a glass of water 30 minutes before a meal can help cut down on your cravings and keep you from overeating. It sounds like if you took some spirulina tablets with this water each time, this might help you lose weight too.

There are so many weight loss programs out there, and I don't know how safe some of them are. Even though spirulina is a natural product, I think it is important to know the company you are purchasing it from.

There can be a wide range of quality when it comes to using these health and nutrition supplements. Also taking 6 tablets at a time a couple times a day could get kind of expensive.

By golf07 — On Jul 28, 2012

I have taken spirulina for about a year now and started taking it more as a general nutritional supplement than to lose weight.

I use the tablets, and they have quite an interesting smell to them. You can sure smell the algae in them, and they are dark green in color.

I can't say that I have noticed any big changes, but think the changes have been subtle, and over a period of time. I used to get very tired right after lunch and always felt like I needed a nap.

Since taking the spirulina, I have more energy in the afternoon. Another thing that it might have helped with is in stabilizing my weight. I used to have about a 5 - 7 pound weight fluctuation. My weight still will fluctuate, but only by 2-3 pounds and it seems more stable.

By donasmrs — On Jul 27, 2012

@turkay1-- I haven't had any side effects from taking spirulina. But don't overdo the dose. I don't think dietary supplements are regulated very well and if you're not sure of the source of the spirulina, you're better off not using it. And even a well know brand might have toxic substances in it. You just never know.

I take a small dose, just 500 mg per day. And there are times when I take a break from it and not take it for a while. I have been able to lose weight on this dose. But don't forget that weight loss is a combination of factors. You can't eat junk food, not exercise, take spirulina supplements and hope to lose weight. Supplements are just one part of a weight loss plan.

Oh and if you are allergic to phenylalanine, you cannot take spirulina because it contains phenylalanine.

By SarahGen — On Jul 27, 2012

@turkay1-- I've been taking spirulina supplements for the past couple of months. I have lost some weight, about five pounds. But I've also started eating healthier and exercising more, so I'm not sure if the spirulina actually contributed to it or not.

My intention was not to lose weight with it anyway. My friend who has been taking it for years suggested it to me as a great energy source. I had been experiencing a lot of fatigue so that's why I started taking it. It has definitely helped in that regard though. I have been feeling a lot more energetic and I think it has been helping me exercise. So indirectly, spirulina is probably helping me lose weight.

I don't see why it wouldn't help with your cravings. I think you should try it. Start with a small dose like the article said and work your way up to higher doses if you have to. Just don't expect very fast weight loss.

By candyquilt — On Jul 26, 2012

I heard about spirulina recently and want to try try it for my cravings. I am a little overweight and I would like to shed a few pounds. But I'm more concerned about my intense sugar and carbohydrate cravings, especially in the afternoon. It feels like no matter great my meals are, I always have to follow up with snack foods or sweets. Especially in the afternoon, I get terrible cravings and sometimes binge eat.

I feel like these cravings are what's getting in the way of me losing my extra weight. Spirulina sounds like a great weight loss supplement and healthy too.

Has anyone tried it? Has it helped you tame your cravings? Also, did you experience any unwanted side effects?

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