Supplements and women's hormones
Inositol for hormonal weight gain What to Check Before You Take It
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed August 20266 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
QUICK ANSWER
Inositol is taken for weight that will not shift, usually on the insulin resistance argument. In a 2025 Italian study, 2,400 mg a day of D-chiro-inositol added nothing to diet alone, and it raised testosterone, androstenedione and LH. If you are taking it, measure those hormones first.
The story turns up on forums most weeks. The weight went on without the diet changing. Standard advice stopped working. Someone suggests it is hormonal, and inositol is the supplement that comes up next.
It is a reasonable idea with a real mechanism behind it. It also has a catch that almost nobody mentions. The form most often sold for weight can push the hormones you were worried about in the wrong direction.
By the Helvy Medical Team · Reviewed by a qualified clinician · 6 min read
As of August 2026. Reflects the D-chiro-inositol study published in Frontiers in Endocrinology in 2025, and the systematic review that informed the 2023 International Evidence-based PCOS Guideline.
1. Why do people take inositol for weight?
Inositol is a sugar-like compound your body makes and you also eat. It sits inside the signal that insulin uses to move glucose into cells. When that signal works poorly, the body makes more insulin to get the same job done. That state is called insulin resistance.
High insulin is genuinely linked with fat storage and with hunger that does not settle. So the logic runs: fix the signal, and weight becomes easier to shift. That is the argument in every post you have read.
Most of the trial evidence comes from women with polycystic ovary syndrome. If that is your situation, our guide to inositol for PCOS covers the ovulation and testosterone data in detail. This guide is for the reader who has not been given a PCOS diagnosis and is taking it for weight.
2. What did the 2025 D-chiro-inositol study find?
This is the part worth reading twice. Researchers in Italy ran an open-label study in 48 women aged 25 to 40. All had a BMI between 26 and 32 and measured insulin resistance. Half took 2,400 mg of D-chiro-inositol a day alongside a reduced-calorie Mediterranean diet. Half followed the diet alone. It ran for four months, and was published in Frontiers in Endocrinology in 2025.
The metabolic results were a draw. Weight, BMI, fasting insulin and fasting glucose all improved. They improved in both groups, by similar amounts. The insulin resistance score fell from 4.6 to 3.25 on the supplement, and from 4.65 to 3.35 on diet alone.
The hormones were not a draw. In the supplement group:
- Total testosteronerose from 42 to 47.5 ng/dL, roughly 1.5 to 1.6 nmol/L in UK units
- Androstenedione, another androgen, rose from 119 to 148.5 ng/dL
- LH, a pituitary hormone, rose from 10 to 12.95 mIU/mL
- Cycle length stretched from 28 days to 32
The diet-only group moved the other way. Their testosterone fell from 40.5 to 28 ng/dL, and their cycles shortened towards 28 days. The authors stopped the study early over the rise in androgens, and titled the paper “opening Pandora’s box”. Their conclusion was blunt: the supplement showed no additional benefit over diet alone.
One small open-label study is not the last word. But it is a reasonable warning. The women in it were taking a supplement for hormonal weight gain, and the hormones moved the wrong way.
3. Which hormones should you measure first?
Here is the practical problem. If you start a supplement without a baseline, you cannot tell later whether it helped, did nothing, or did what the Italian study saw. You are guessing from how you feel, and weight is a noisy signal.
Four of the markers that moved in that study are measurable, and they read best together:
- Total testosterone — the headline androgen number
- SHBG — the protein that decides how much of it is active
- Free androgen index — testosterone and SHBG combined into one figure
- LH and FSH— the pituitary pair behind your cycle
Our Hormone Balance panel (£99) measures those five from a home finger-prick sample, analysed by UKAS-accredited UK laboratories. Androstenedione is not in it, and neither is fasting insulin or HOMA-IR. Those are a GP or a custom build, and it is worth saying so plainly rather than implying otherwise.
On the blood sugar side, HbA1c is the marker most worth having. It reflects your average blood sugar over roughly three months, so a single meal cannot flatter it. We measure it in the Advanced Heart Health panel (£159). There is more on the wider picture in our guide to testing for insulin resistance. Blood markers describe what is happening. They do not diagnose a condition on their own.
4. Is myo-inositol different from D-chiro-inositol?
Yes, and the difference matters more than the label suggests. Most UK products sell the two together, often in a 40 to 1 ratio of myo-inositol to D-chiro-inositol. That ratio is meant to copy the balance found in the ovary.
The 2025 study used D-chiro-inositol alone, at 2,400 mg a day. That is a high dose of the form usually given in small amounts. Most combination products contain nothing like it. So the finding is a reason to read the label, not a reason to panic about every capsule.
It is also worth knowing how lightly this whole category is regulated. The NHS Specialist Pharmacy Service puts it in one sentence:
“Food manufacturers are not required to prove the safety or efficacy of their products before placing them on the market.”
— NHS Specialist Pharmacy Service, Understanding food supplements
The same page notes that amounts can vary between batches. A dose on a label is a claim, not a guarantee. That is another argument for measuring rather than assuming.
5. What if your weight gain is not PCOS?
This is the gap the forums skip. Inositol is a PCOS supplement that gets borrowed by people who have never been assessed for PCOS. Two other explanations are far more common, and both are measurable.
AN UNDERACTIVE THYROID
The NHS lists “putting on weight” among the common symptoms, alongside tiredness and feeling the cold. It is checked with a thyroid blood test looking at TSH and thyroxine. No supplement substitutes for that check.
PERIMENOPAUSE
Weight that redistributes towards the middle in your forties is a common perimenopause pattern. Our menopause hub covers what blood tests can and cannot tell you at that stage, which is less than most people expect.
SOMETHING SIMPLER
Sleep debt, a new medication, alcohol, or a quiet drop in daily movement. None of these are hormonal, and all of them are worth ruling out before you spend money on capsules. Our guide to unexplained weight gain works through the list.
If the weight change is rapid or came with other new symptoms, see your GP rather than starting a supplement. That is the fastest route to an answer, and it is free.
Frequently asked questions
Does inositol help you lose weight?
The evidence is weak. In the 2025 Italian study, weight and BMI fell by similar amounts whether women took 2,400 mg of D-chiro-inositol or followed the diet alone. The systematic review behind the 2023 International Evidence-based PCOS Guideline found no meaningful difference in BMI either.
Can inositol raise testosterone in women?
High-dose D-chiro-inositol did in one 2025 study. Total testosterone, androstenedione and LH all rose over four months, and the researchers stopped the study early because of it. That is a single small study, and the opposite of what most inositol research in PCOS reports.
Which inositol should I take, myo or D-chiro?
Most UK products combine both, usually at 40 parts myo-inositol to 1 part D-chiro-inositol. The 2025 study that found rising androgens used D-chiro-inositol on its own at a high dose. Check the label for which form you are actually buying, and how much.
What blood tests should I do before taking inositol?
A baseline of total testosterone, SHBG, free androgen index, LH and FSH covers the hormones the research shows moving. HbA1c covers the blood sugar side. Repeat them after three to six months, and you have a real before and after rather than a guess.
Is hormonal weight gain always PCOS?
No. An underactive thyroid and perimenopause are both common explanations, and neither responds to a PCOS supplement. Thyroid function is checked with TSH and thyroxine. If your weight changed quickly, or came with other new symptoms, speak to your GP.
Measure it, do not guess it
Our Hormone Balance panel (£99) measures FSH, LH, SHBG, total testosterone and free androgen index. Home finger-prick kit, results usually within 5 working days of the lab receiving your sample, from UKAS-accredited UK laboratories.
Medical disclaimer:This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. The studies cited measure population-level effects and may not predict an individual response. Do not start, stop or change any supplement or medication based solely on this article — consult your GP or a qualified healthcare professional. All Helvy blood tests are processed by UKAS-accredited UK laboratories to ISO 15189.
Last updated: August 2026 · By Helvy · Medically analysed at UKAS-accredited UK laboratories
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