Chlorella for dogs and how to use it safely

Yes, dogs can have chlorella. It is a plain green alga, it isn't toxic to dogs, and most dogs take it without any trouble at the amount on the pack. The two things that can happen are loose stools or wind when a dog starts on a full serving straight away, and green-tinged poo, which looks alarming but is harmless.

Start with a small amount and build up over a week or so. Talk to your vet first if your dog is on regular medication, has an autoimmune or thyroid condition, is pregnant or nursing, or has kidney disease. Chlorella is a food supplement. It isn't a treatment for an ill dog.

What chlorella is

Chlorella is a single-celled freshwater green alga. The species sold for dogs and people is mostly Chlorella vulgaris. Each cell is tiny, and it is wrapped in a tough wall that a dog can't digest well, so good chlorella is processed to crack that wall open. Labels call this broken cell or cracked cell chlorella.

It is high in protein and has all ten of the amino acids a dog has to get from food. It is also one of the richest food sources of chlorophyll, the green pigment in plants, and it has carotenoids such as beta-carotene and lutein. You will also see chlorella growth factor, or CGF, on labels. That is a name for an extract of the cell's own nucleic acids and peptides, and there is no dog research on it.

Chlorella is not a seaweed. Seaweeds such as kelp are large algae from the sea, and some are very high in iodine. Chlorella is microscopic and grown in tanks or ponds.

How much chlorella to give a dog

Go by the pack of the product you have, because powders differ in what else is in them. Our Microalgae Blend for Mature Dogs is a 115 g jar of organic European Chlorella vulgaris and Nannochloropsis, and this is the daily amount printed on it.

Dog size	Daily amount	Measure
Small dog	3 g	½ to 1 teaspoon
Medium dog	6 g	1½ to 2 teaspoons
Large dog	10 g	2 to 3 teaspoons

The pack asks owners to start with small amounts and work up to that serving. In practice that means a pinch for the first few days, then a little more each day while the stools stay normal. If they go soft, drop back to the last amount that suited your dog and hold it there for a few days.

Mix it into wet food or a spoon of plain yoghurt. If you also feed spirulina, use half the serving of each rather than a full dose of both. Once the jar is open, use it within six months.

What chlorella does for dogs

Most chlorella research is in people, mice and rats. The best dog study is a controlled trial in healthy Beagles, and it tests the same two kinds of alga that are in our blend.

Gut and digestion

Cabrita and colleagues (2023, Frontiers in Veterinary Science) fed 12 healthy adult Beagles diets with Chlorella vulgaris, Nannochloropsis oceanica or a third alga at up to 1.5% of the food. The six dogs in the digestion part of the trial digested slightly more of their protein with chlorella (73.9% against 70.6% on the plain diet). Their faeces became a little more acidic, with more of the short-chain fatty acids that gut bacteria make from fibre. That is how a prebiotic works, by feeding the bacteria, and the mix of gut bacteria shifted, including a rise in Turicibacter. Nannochloropsis made the stools slightly firmer. No dog had vomiting, diarrhoea or weight loss.

The same trial found something the marketing leaves out. Offered two bowls, the dogs preferred food without chlorella or Nannochloropsis in it. Two of our reviewers mix it into yoghurt treats, and a fussy dog may need it in something tasty.

The immune system

The best human study is a trial in 51 healthy adults in Korea (Kwak and colleagues, 2012, Nutrition Journal). Eight weeks of chlorella tablets raised the activity of natural killer cells, the white blood cells that attack infected cells, and raised interferon-gamma, a signal the immune system uses against viruses. Nobody has run that test in dogs, so we treat immune support as likely but unproven for them.

Heavy metals and other toxins

Chlorella binds metals and some pollutants in the gut. Two named animal studies tested this. Mice fed a related alga, Parachlorella beijerinckii, at 5 to 10% of their diet passed more methylmercury in their faeces and urine over three weeks and had less mercury in their kidneys and brain (Uchikawa and colleagues, 2011, Journal of Toxicological Sciences, a study partly run by a chlorella maker). In rats, chlorophyll from chlorella cut how much dioxin was absorbed from food (Morita and colleagues, 2001, Environmental Health Perspectives).

There is no trial of this in dogs, and the mouse doses were far higher than any pack serving. If your dog has eaten something poisonous, that's a call to your vet or a poison line now, not a job for a supplement.

Skin and coat

Three of the 10 reviews of our blend mention the coat. "Since putting this in my dogs food I have noticed their coats are much softer and smoother," wrote Danielle C. on 31 March 2023. Sanne R. wrote on 28 March 2023 that the fur on their dogs was "Shinier and softer!" The Nannochloropsis in our blend adds omega-3 fats, including EPA, which matter for skin.

A coat change needs new hair to grow through, so expect weeks rather than days. Itching or sore skin needs your vet before any supplement.

Chlorella for older dogs

We make our blend for mature dogs, and several of its reviews come from owners of older ones. Jennie wrote on 25 June 2026 that it "works great for my 11 year old lab! She seems to have more energy and be more comfortable." V.R. gives it to an almost 16-year-old terrier mix with stiff joints, and wrote on 1 January 2026 that the dog "still limps occasionally and is stiff after lying in the same position but overall seems much improved".

The reasoning is the antioxidants. Chlorella has chlorophyll, vitamin C, beta-carotene, lycopene and lutein, and older bodies deal with more oxidative wear. No study has tested chlorella on memory or ageing in dogs, though, so we can't promise a sharper mind. The reviews above talk about energy and comfort.

Active and working dogs get the same nutrients, and the protein and omega-3 suit a dog that runs all day. Joanne B., who feeds a raw diet, wrote on 3 April 2023 that her nearly 9-year-old Golden Retriever "runs and plays like a dog half her age". A limp that doesn't settle, or stiffness that is getting worse, still needs your vet.

Chlorophyll and bad breath

Yes, you can give a dog chlorophyll, and chlorella is a whole-food way to do it. The liquid and tablet chlorophyll sold for dogs is usually sodium copper chlorophyllin, a water-soluble form made from plant chlorophyll. It is widely used as a food colouring.

Chlorophyll is the reason chlorella turns up in breath products. We know of no study that shows it fixing bad breath in dogs. Most bad breath in dogs comes from plaque and tartar on the teeth, and gum disease, so a dog whose breath has turned bad should have its mouth checked. Red gums or a loose tooth need a vet visit.

Side effects and when to check with your vet

For most healthy dogs, the side effects are mild digestive upsets that come from too much too fast.

• Loose stools or wind in the first days. Go back to a smaller amount.
• Green or dark green poo. That's the chlorophyll, and it stops when the chlorella does.
• A dog who leaves food with chlorella in it. Try a smaller amount or a tastier carrier.

Check with your vet before you start if your dog takes regular medication, has an autoimmune disease, a thyroid problem, kidney disease or a known allergy to iodine or mould, or is pregnant or nursing. Chlorella also contains vitamin K, which matters for the rare dog on a blood thinner.

Puppies already get everything they need from a complete puppy food. Our blend is made for mature dogs, so for a puppy ask your vet before adding it.

Quality is the other risk. Chlorella takes up what is in the water it grows in, so a product from dirty water can carry heavy metals. Some algae ponds can also be contaminated with microcystins, toxins from blue-green algae.

Chlorella or spirulina for dogs

Chlorella and spirulina are the two best-known kinds of algae for dogs, and they are often sold together. Chlorella is a true green alga with a tough cell wall that needs cracking. Spirulina is a cyanobacterium, often called blue-green algae, with a soft wall that dogs digest easily. It is higher in protein and has phycocyanin, the pigment behind blue spirulina.

Chlorella has more chlorophyll, and the mercury and dioxin studies above were done with chlorella. Dogs can have both. Our advice is half the serving of each.

Choosing a chlorella product for your dog

Look for broken cell chlorella with nothing added except what the label explains. The maker should say where it is grown and test it for heavy metals and microcystins. Human chlorella tablets are fine for a dog in principle, but check them for sweeteners and added herbs first, and work out the dose from the tablet weight.

Our Microalgae Blend for Mature Dogs is organic Chlorella vulgaris and Nannochloropsis grown in Portugal, with nothing else in the jar. Its 10 reviews average five stars. The chlorella gives it chlorophyll and protein. The Nannochloropsis adds omega-3 with EPA, which plain chlorella lacks.

Questions owners ask about chlorella

Is chlorella safe for dogs?

Yes, for healthy dogs at the pack amount. Build up slowly and buy from a maker that tests for contaminants. Ask your vet first if your dog has a medical condition or takes medication.

Can dogs have chlorella tablets?

Yes. Chlorella powder is easier to mix in, but tablets work too. Crush them into food or offer one as a treat if your dog will take it. Use a plain chlorella tablet with no sweeteners or herbs added, and match the grams to the dosing above.

How long does chlorella take to work in dogs?

There is no dog study that measures this. A coat change needs new hair to grow through, which takes weeks. Our advice is to give it at least two months at the full serving before you decide whether it suits your dog.

Can chlorella cause diarrhoea in dogs?

It can if you start too high. Cut back to a pinch and build up again more slowly. Diarrhoea that lasts more than a day or two, or comes with vomiting or blood, is a vet visit.

References

• Cabrita ARJ et al. (2023). Effects of microalgae as dietary supplement on palatability, digestibility, fecal metabolites, and microbiota in healthy dogs. Frontiers in Veterinary Science 10:1245790.
• Kwak JH et al. (2012). Beneficial immunostimulatory effect of short-term Chlorella supplementation. Nutrition Journal 11:53.
• Uchikawa T et al. (2011). Enhanced elimination of tissue methylmercury in Parachlorella beijerinckii-fed mice. Journal of Toxicological Sciences 36(1):121-126.
• Morita K et al. (2001). Chlorophyll derived from Chlorella inhibits dioxin absorption from the gastrointestinal tract and accelerates dioxin excretion in rats. Environmental Health Perspectives 109(3):289-294.