Can intermittent fasting cause hormonal imbalances in women?

Ask Dr. Jason Fung

There are tons of questions about intermittent fasting, like these:

  • Can intermittent fasting cause hormonal imbalances in women?
  • As Metformin prevents your liver from producing sugar, will your liver be able to clean out the accumulated sugar?

Dr. Jason Fung is one of the world’s leading experts on fasting for weight loss or diabetes reversal. Here are a his answers to those questions and more:

I’ve read that IF can cause hormone imbalances with women, is this true?

While I know this is one study1, I didn’t know if you’ve come across this through your program with other women? I’ve read about similar problems online with other women.

The reason I am asking is because I have been doing IF, 36-hour fasts every other day for 8 weeks with success. I have lost 15 lbs (7 kg) and my blood pressure has dropped. However, I am noticing hormonal problems with missed periods, and dry skin. Also a friend of mine, who is also doing IF, has begun to experience hot flashes. We are both in our late 40’s, and while we are getting close to menopause, it seems a bit early, and for us to suddenly start experiencing these symptoms when we began IF seems too coincidental.

While I am pleased with the results and I intend to continue with IF, I am wondering if you have any recommendations or suggestions? Perhaps a more modified intermittent-fasting approach?

Thank you,

Women can fast. That study is on rats. If you are a young rat, then maybe you shouldn’t fast. If you are a human adult, then yes, you may fast. We have had several thousand years of human history to guide us that yes, women may fast with equal efficacy to men. I’ve treated hundreds of women. Yes, some have problems fasting, but so do some men. There’s no difference.

Dr. Jason Fung

Learn more about women and fasting

Since Metformin prevents your liver from producing sugar, will your liver be able to clean out the accumulated sugar?

I’ve been on strict LCHF for 5 months religiously per page 4 eating plan. Lost 20 lbs (9 kg) during the first 6 weeks, then stopped. I stuck with it and finally decided to go on Metformin a couple of weeks ago per Dr. William Wilson in Keto Clarity.

I read your info on Dawn Phenomenon and I’m concerned that Metformin will prevent my liver from dumping all the stored sugar. Just started intermittent fasting yesterday to jolt my system. Blood glucose was 165 mg/dl (9.2 mmol/l) before metformin and is now hovering around 135-155 mg/dl (7.5-8.6 mmol/l). I’ve never taken any other medicines for type 2 diabetes and don’t have any other symptoms of type 2 diabetes.


Metformin blocks gluconeogenesis. It is neither particularly harmful nor helpful for type 2 diabetes. It lowers blood glucose but does nothing for diabetes.

Dr. Jason Fung

Learn more about the dawn phenomenon – why are blood sugars high in the morning?



Intermittent Fasting for Beginners

Earlier Q&A sessions with Dr. Fung:

Many more questions and answers:

Intermittent Fasting Q&A

Q&A videos

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    Everything in moderation?

Top Dr. Fung videos

  • Diet Doctor Podcast #64 with Jason Fung
    Part 8 of Dr. Jason Fung's diabetes course
    The essential problem with type 2 diabetes

More with Dr. Fung

Dr. Fung has his own blog at He is also active on Twitter.

His book The Obesity Code is available on Amazon.

The Obesity Code

His new book, The Complete Guide to Fasting is also available on Amazon.


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