Things to Know Before Taking Inositol Supplement

Inositol is a popular nutritional supplement. Find out what are the dosages for different conditions, how it interacts with common prescription medications, and other things you should be careful of when taking inositol supplement.

Dosage – How Much Inositol Should You Take

There is no general recommendation for inositol supplements. Instead, your dosage of inositol depends largely on the condition for which you are taking it.

Most inositol supplements on the market contain myo-inositol. This type of inositol is also the one, which is most commonly found in natural sources and most extensively studied for use in different medical conditions.

So, if the supplement’s label doesn't state the exact form of inositol, you are safe to assume that your supplement contains myo-inositol.

Likewise, below described dosages and recommendations apply to myo-inositol. If a certain recommendation is for another type of inositol (for example d-chiro inositol), this is clearly specified in the text.

Common dosages for inositol supplements are:

For Improving the Symptoms of Polycistic Ovary Syndrome (PCOS)

Inositol has been extensively studied for the use in PCOS. Studies have used different dosages (1), but most common dosage appears to be 4 g per day (divided into 2 grams twice daily). One study showed that 4 grams of myo-inositol work as well as an established PCOS drug Metformin at a dose of 1.5 grams daily (2).

Another commonly seen option in PCOS is combining the use of myo and d-chiro inositol. These 2 isomers of inositol have different actions in the body. Myo-inositol improves the function of ovaries, while d-chiro inositol decreases peripheral hyperinsulimia (excess level of insulin in the body’s extremities).

Studies have shown that the combination of myo and d-chiro inositol works particularly well for obese women with PCOS. In this group, it reduces the risk of metabolic disease and balances hormones much more effectively that supplementation with myo-inositol alone (3).

The ratio of supplemental myo-inositol versus d-chiro-inositol should be about 40:1, which is the ratio of these two substances in the body.

Doses used in studies were:

1.1 g myo-inositol plus 27.6 mg of d-chiro-inositol


550 mg myo-inositol plus 13.8 mg d-chiro inositol

Several studies have also indicated that inositol works even better for PCOS when combined with alpha lipoic acid at 800mg daily (5), (6).

For Reducing Anxiety and Panic Attacks

Animal studies (6) have shown that inositol has anti-anxiety (anxiolytic) properties.

Most commonly stated dose for anxiety is between 12 grams and 18 grams per day. This is obviously a very large dose, so you should start slowly and build your dose 1 gram at a time.

Inositol also reduces the number and severity of panic attacks; although it takes a while for the effects to take place. One study (7) indicated that you should wait at least a month before evaluating the effects of inositol supplementation on panic disorder.

The dosage used in research for help with panic attacks was 12 grams of inositol daily.

For Depression

Dosage used for depression is typically 12 grams of inositol daily. This dose has been shown to improve the symptoms of depression after 4 weeks (8).

It looks like inositol doesn’t work for depression in people that don’t respond well to SSRIs medications (9).

For Sleep Problems and Insomnia

Many people take inositol for insomnia and disrupted sleep and there are reports showing that it often helps. This can be explained by the way inositol affects neurotransmitters GABA and serotonin, which are both linked to our quality of sleep.

Doses used for sleep problems are typically around 2 grams of inositol daily. Like with other conditions, effects of inositol on sleep aren’t seen at once, but they build up in time.

For Obsessive Compulsive Disorder (OCD)

Inositol is often used for treating obsessive compulsive disorders. It has been shown to be effective at 18 grams per day (10).

Inositol doesn’t work for people with OCD who don’t respond to SSSRIs (11).

When and How To Take Inositol

It is always best if you start inositol supplementation slowly with a small dose. Wait a while to get used to it and increase the dose 1 gram at a time. Some conditions require quite large doses, so it will take you a while to get there. However, by not rushing things you have significantly better changes of not experiencing any side effects, such as gastrointestinal upset.

Divide your daily dose into several smaller doses and take them evenly through the day. It is best if you take inositol on an empty stomach to maximize its absorption.

Most inositol supplements are in the form of fine white powder. This powder can be bought in bulk or prepackaged into capsules. If you are taking large daily doses of inositol, bulk powder is probably the way to go since it is usually considerately cheaper.

Inositol powder is usually taken dissolved into water or fruit juice. Water with inositol has a mildly sweet taste that most people find quite pleasant.

There is also another form of inositol, which comes in the form of soft gels. Inositol in these gels is prepared in a way that increases its absorption. If you are taking this type of inositol supplement, your needed dose is about 30% of inositol in powder form (for example, you would take 4 grams instead of 12 grams to achieve the same effects).

Inositol supplements should be stored in a cool, dry place and away from direct sunlight.

Safety and Side Effects

Inositol is considered a very safe nutritional supplement. It is soluble in water, so it doesn't build up to potentially dangerous concentration in the body.

Most people experience few or none side effects from inositol. Most common side effects are loose stools at the beginning of supplementation, which resolve as your body gets used to inositol.

Other reported side effects are nausea, headaches, fatigue and dizziness.

Some people also notice increased sweating that usually resolves with time.

You can decrease the risk of side effects if you start with smaller dose that you gradually increase.

Who Should be Cautious When Taking Inositol

There have been reports about inositol triggering a mania episode in people with bipolar disorders. Some of these cases involved the use of several supplements alongside inositol, so it is not clear which supplement set off the symptoms of mania. Still, it is safer to avoid using inositol if you have a bipolar disorder.

Pregnant and Breastfeeding Women

Inositol has been used in several clinical studies as a supplement for inducing ovulation and achieving pregnancy in women with PCOS and women undergoing IVF. It has been shown that both myo-inositol alone and the combination of myo and d-chiro inositol in ratio 40:1 are able to increase pregnancy rate and improve oocyte (egg cell) and embryo quality.

Some of these studies continued with the use of inositol till the end of pregnancy. These studies have found that inositol significantly reduces the rates of gestational diabetes – especially in the PCOS group.

The doses used for preventing gestational diabetes were as high as 4 grams daily. However, it should be noted that in higher doses inositol may cause uterine contractions, which may lead to miscarriage. It might be best to avoid inositol supplementation in pregnancy. If you still decide to do so, keep the dosage low.

Inositol use hasn't been studied in breastfeeding women. However, it should be noted that inositol is naturally contained in human breast milk, so negative side effects to the baby seem unlikely.


Inositol is being used for treating children with several psychiatric disorders, such as depression and OCD. Side effects seem to be similar to the ones in adults; mostly loose stools and mild stomach upset.

It is important that the dose given to children is adjusted according to body weight, so typically it will be much smaller than adult dose.

If you decide to give inositol to a child, you must always do so under supervision of qualified medical professional.

Interactions With Prescription Medications

SSRIs Medications

SSRIs are medications used for treating conditions, such as depression and OCD. They work by raising the level of neurotransmitter serotonin in the brain. Inositol likewise works by raising serotonin levels.

Theoretically, if you take these medications and inositol together, this might lead to the so called serotonin syndrome. This syndrome is characterized by agitation, high body temperature, diarrhea, tremor, and sweating. Serotonin syndrome is very dangerous and can be potentially fatal.

Phytic Acid (Inositol Hexaphosphate or IP6)

Phytic acid (known also as IP6) is a derivative of inositol with 6 phosphate groups. It is found in cereals and grains. It has a very low bioavailability, which means that our bodies are able to use only small portion of this substance that we get from food.

The combination of myo-inositol and IP6 appears to have anti-cancer effects (12), (13). IP6 has also been found to augment the action of certain chemotherapeutics (for example adriamycin and tamoxifen), so it is sometimes used as an adjuvant to chemotherapy (14).

One placebo controlled study (15) examined women with breast cancer, who have taken IP6 and inositol alongside chemotherapy. Results have shown increased quality of life, decreased side effects, and preserved leukocyte and red blood cell count in this group compared to control group.


Myo-inositol is sometimes used for increasing fertility. Melatonin has been shown to boost the effects of myo-inositol on infertile women and increase the amount of mature oocytes (egg cells).


Carmazepine is a medication, used for treating epilepsy and nerve pain, such as pain in trigeminal neuralgia. Carmazepine reduces inositol levels in the brain. It is currently unclear how supplemental inositol affects the effect of carmazepine, so people taking it should stay away from inositol supplements.


Lithium is used for managing manic episodes of bipolar disorder. Lithium decreases the level of inositol in the brain and inositol taken as a supplement decreases the effects of lithium. If you are taking lithium, avoid using inositol as it will decrease its effectiveness.

Valproate and valproic acid

These medications are used for treating epilepsy and bipolar disorder. Inositol supplements decrease their effectiveness, so don't use inositol if you are being treated with vaproate or valproic acid.

Inositol with other Herbs, Supplements and Foods

5 HTP and St. John's Wort

5HTP and St. John's wort are two supplements that are commonly used for treating depression and insomnia. They both work by raising the levels of serotonin in the brain (similarly to SSRIs medications).

Since inositol also increases the levels of serotonin in the brain, the effects might add up to potentially dangerous levels. This may lead to the so-called serotonin syndrome. For that reason, it is recommended that you don't take inositol together with either 5HTP or St.John's wort.


Inositol is often taken together with choline. Choline is related to B group vitamins and is precursor for the neurotransmitter acetycholine, which is associated with memory, learning and cognitive abilities in general.  Taken together, inositol and choline support overall brain health and mental function.

The body also uses choline and inositol to create lecithin, which is an important component of cellular membranes. Besides promoting cell health, lecithin also facilitates the transfer of fats through the organism, helps regulate cholesterol levels and prevents fat build up in the liver.

You might also be interested in:

  1. Vittorio Unfer et al. Effects of Inositol(s) in Women with PCOS: A Systematic Review of Randomized Controlled Trials. (2016)
  2. Fruzzetti F et al. Comparison of two insulin sensitizers, metformin and myo-inositol, in women with polycystic ovary syndrome (PCOS). (2016)
  3. M. Nordio and E. Proietti. The Combined therapy with myo-inositol and D-Chiro-inositol reduces the risk of metabolic disease in PCOS overweight patients compared to myo-inositol supplementation alone. (2012)
  4. Cianci A et al. D-chiro-Inositol and alpha lipoic acid treatment of metabolic and menses disorders in women with PCOS. (2015)
  5. Rago R et al. Effect of myo-inositol and alpha-lipoic acid on oocyte quality in polycystic ovary syndrome non-obese women undergoing in vitro fertilization: a pilot study. (2015)
  6. O. Kofman et al. The anxiolytic effect of chronic inositol depends on the baseline level of anxiety. (2000)
  7. Benjamin J et al. Double-blind, placebo-controlled, crossover trial of inositol treatment for panic disorder. (1995)
  8. Levine J et al.  Double-blind, controlled trial of inositol treatment of depression. (1995)
  9. Nemets B et al. Inositol addition does not improve depression in SSRI treatment failures. (1999)
  10. Fux M et al. Inositol treatment of obsessive-compulsive disorder. (1996)
  11. Fux M et al. Inositol versus placebo augmentation of serotonin reuptake inhibitors in the treatment of obsessive-compulsive disorder: a double-blind cross-over study. (1999)
  12. Somasundar P et al. Inositol hexaphosphate (IP6): a novel treatment for pancreatic cancer. (2005)
  13. Tantivejkul K et al. Inositol hexaphosphate (IP6) inhibits key events of cancer metastasis: II. Effects on integrins and focal adhesions. (2003)
  14. Tantivejkul K et al. Inositol hexaphosphate (IP6) enhances the anti-proliferative effects of adriamycin and tamoxifen in breast cancer. (2003)
  15. Bacić I et al. Efficacy of IP6 + inositol in the treatment of breast cancer patients receiving chemotherapy: prospective, randomized, pilot clinical study. (2010) 

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