Summary: Do you have weird digestive symptoms and anxiety or depression? Consider trying inositol (affiliate link), especially if the symptoms started after antibiotics.

Epistemic status: I did some research on this 10 years ago and didn’t write it down. In the last nine months I recommended it to a few people who (probably) really benefited from it. My track record on this kind of suggestion is mixed; the Apollo Neuro was mostly a dud but iron testing caught a lot of issues. 


Inositol is a form of sugar. It’s used in messaging between cells in your body, which means it could in theory do basically anything. In practice, supplementation has been found maybe-useful in many metabolic and psychiatric issues, although far from conclusively. 

There are a few sources of inositol: it’s in some foods, especially fruit. Your body naturally manufactures some. And some gut bacteria produce it. If your gut bacteria are disrupted, you may experience a sudden drop in available inositol, which can lead to a variety of symptoms including anxiety and depression.


Inositol deficiency (probably) hit me hard 9 years ago, when I went on a multi-month course of some very hardcore antibiotics to clear out a suspected SIBO infection.

Some background: My resistance to Seasonal Affective Disorder has been thoroughly tested and found triumphant.  At the time I took those antibiotics I lived in Seattle, which gets 70 sunny days per year, concentrated in the summer. This was a step up from my hometown, which got 60 sunny days per year. I briefly experimented with sunshine in college, where I saw 155 sunny days per year, a full 75% of the US average. The overcast skies never bothered me, and I actively liked Seattle’s rain. So when I say I do not get Seasonal Affective Disorder or light-sensitive depression, I want you to understand my full meaning. Darkness has no power over me. 

That is, until I took those antibiotics. I was fine during the day, but as soon as sun set (which was ~5PM, it was Seattle in January) I experienced crushing despair. I don’t know if it was the worst depression in my life, or just the most obvious because it went from 0 to doom 15 minutes. 

Then I started taking inositol and the despair went away, even though I was on the antibiotics for at least another month. After the course finished I took some probiotics, weaned off the inositol, and was fine. 

About six months ago, my friend David MacIver mentioned a combination of mood and digestive issues, and I suggested inositol. It worked wonders.

He’s no longer quite so deliriously happy as described in the tweet, but still describes it as “everything feels easier”, and every time he lowers his dose things get worse. So seems likely this is a real and important effect

He’s also tried probiotics. It took several false starts, but after switching brands and taking them very consistently he was able to lower his dosage of inositol, and the effects of going off it are less dramatic (although still present).

He has a fairly large twitter following, so when he tweeted about inositol he inspired a fair number of people to try it. He estimates maybe 50 people tried it, and 2-5 reported big benefits. So ballpark 4-10% response rate (of people who read the tweet and thought it looked applicable). And most people respond noticeably to the first dose (not me, I think it took me a few days, but most people), so it’s very easy to test. 

A second friend also got very good results, although they have more problems and haven’t tested themselves as rigorously as David, so causality is more questionable. 

Fun fact: because inositol is a cheap, white, water soluble powder it’s used as a cutting agent for multiple street drugs. It’s also the go-to substitute for cocaine in movies. So if cocaine, heroin, or meth have weirdly positive effects on you, might be worth checking out.


Anything with a real effect can hurt you. Even that totally safe magic bracelet I recommended maybe gave someone nightmares. But as these things go, inositol is on the safer end to experiment with. The fact that it’s both a natural food product and produced endogenously gives you good odds, especially compared to cocaine. OTOH the fact that it has a lot of sources makes it harder to dose – after a few months David found that his initial dose was too high and induced brain fog, and he needed to lower it. 

I have a vague impression that quality isn’t an issue with inositol the way it is with some vitamins, so I just linked to the cheapest ones. 

In terms of dose: standard dosage is 0.5- 2g/day. David started at high end of that but is now down to 0.5-1g. I can’t remember what I did. If you try it, start small and experiment. 

If you do try it, I’d love if you filled out this form letting me know how it went.

Thanks to David Maciver for sharing his data. 

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5 comments, sorted by Click to highlight new comments since: Today at 6:03 AM

Of interest: Inositol tastes sweet (and otherwise neutral) and is relatively heat stable and soluble; yet it actually has a desirable impact on glucose sensitivity, diabetes, inflammation and obesity.

Meaning you don't have to down it in pill form, which tends to be more expensive - but you can get the powder, and use it as a healthy sugar replacement (within safe dosing limits - don't like, bake cake with it, but I found it a good option to positively affect the flavour other powders I want to down, where I would have otherwise used stevia, which is dubious in large quantities, or erythrol, which can cause gastrointestinal upset; this way, my sugar replacements are more spread out). Kills two birds with one stone.

I've had success using inositol to treat romantic limerance / obsession. Full writeup here. In short, I tried it out of a theory that brain patterns of people in love is similar to OCD and inositol is used off label to treat OCD. At the peak I took 8g a day. Taking powder inositol under the tongue was faster and more intense but shorter lasting.

Of the people who saw my post, some tried it, and only one other person has told me it helped them get over someone while 2 or 3 people told me it didn't help at all.

It has a calming effect for me in general.
I still occasionally take 0.5g under the tongue sometimes when I feel like I need to. I try to avoid it because on reflection choosing not to be in love was a bit personality suicide, wasn't actually what I valued, but I think it's still good that I have the choice, and that I was able to think about it from a clearer mind

"A" graded evidence on examine for PCOS symptoms and "fertility". "B" for anxiety (slight improvement for anxiety, moderate for "panic symptoms") . 


Now, I have a lot of TBI's in my past and originally came across this for "OCD symptoms" , I wont bore you with details but it would definitely be considered sub clinical and not meeting DSM criteria for an actual OCD diagnosis. I came across inositol I think in 2013 or 14, either the nootropics or MTHFR sub reddits. 


"C" rating on examine but that's because they only have one human study linked. Up to 12 grams a day oral in adults usually only results in GI upset although a thorough long term and dose dependant study has yet to be done so we can't definitively say its "safe and harmless". My own regime is 2 grams in the morning and 2 in the afternoon for months at a time (been doing this for probably a decade) with a few weeks off every now and then when I forget to order more. I do twice yearly labs and so far my CBC and CMP are unremarkable, 38 male, testosterone levels where they need to be.


Honestly I can't say anything I get from it isn't just placebo, even this far in. I'm not keeping "weird sort of OCD / anxiety" symptom journals when I don't have it and I randomly arrives at the current 4 grams a day (I get 1 gram tablets so two is just easy to remember and dispense into my supplement case)

If you have the power to change the Google form, by the way, one of its questions is "What dose did you take (in mg)? 0.5, 1, 1.5, 2+"

Presumably this should read "(in g)", and it would also help if it were explicitly stated as being "per day".

Thanks for posting this! I'd vaguely planned to try it after seeing David's tweet, but never got around to it.

I see Healthline says there is little evidence on long-term effects - any thoughts on how long to take it?