Does chlorella cause diarrhea, bloating or gas?

Yes — diarrhea is one of the most commonly reported effects of chlorella, alongside nausea, cramping, gas and green-tinged stools, according to a government drug database. These are usually mild and tied to how much you take, not a sign that something is wrong; the same source describes chlorella overall as "usually well tolerated."

What the reporting actually says

A LactMed monograph — a US National Library of Medicine reference on supplements and medications — reports that chlorella "is usually well tolerated but can cause nausea, diarrhea, abdominal cramping, flatulence and green stools." It's a narrative summary of published case reports and the existing literature, not a controlled trial measuring how often each effect happens or at what dose, so we can't give you a percentage or a specific mg threshold — only that these are the effects on record.

Why chlorella affects digestion

Chlorella is a whole-cell algae supplement that's roughly half protein by dry weight, with fiber, chlorophyll and other plant compounds alongside it. Introducing a new source of fiber and dense plant material can cause gas, bloating or looser stools while your digestive system adjusts — a common pattern with concentrated plant supplements generally, not something specific to a toxic effect of chlorella. The green tinge some people notice in their stool comes from chlorophyll passing through the digestive tract; it's a cosmetic effect, not a sign of a problem.

Taking it on an empty stomach

We haven't found a trial comparing chlorella taken with food against chlorella taken on an empty stomach. If nausea or stomach upset shows up, taking it with a meal is a reasonable adjustment to try — see when is the best time to take chlorella for the full picture on timing, which is thin either way.

When it's more than mild

Persistent or severe diarrhea, or diarrhea alongside other symptoms like a rash or difficulty breathing, isn't something to wait out — stop taking it and talk to a doctor. Severe allergic reactions to chlorella, including anaphylaxis, have been reported, though uncommonly; see chlorella side effects for the full list of documented effects, including the rarer, more serious ones.

Questions people ask

Does chlorella make you poop?

It can. Diarrhea and looser stools are among the most commonly reported digestive effects, alongside gas and cramping, according to a government drug database.

Why does chlorella cause gas?

Chlorella's fiber and dense cell-wall material are the likely reason, the same way any new concentrated plant supplement can cause gas while your gut adjusts. We haven't found a trial that isolates the mechanism specifically for chlorella.

Can chlorella cause nausea?

Yes — nausea is listed alongside diarrhea, cramping and flatulence as a commonly reported effect in the same government drug database summary.

Can chlorella upset your stomach if taken on an empty stomach?

We haven't found a trial testing that specifically. Taking it with food is a reasonable adjustment if an empty stomach seems to make things worse for you.

Related reading: chlorella side effects, how much chlorella should you take a day, and best time to take chlorella.