Is Insulin Resistance Causing Your PCOS?

By Clare Goodwin

Last updated: December 17, 2021

Insulin resistance and PCOS commonly occur together. Have you got PCOS, but never been tested for insulin resistance? Or maybe you have been tested, but your doctor has told you that your blood sugar is normal? If so, you may have been left wondering what’s causing your PCOS.

During my second year at university we did an experiment where were measured our blood glucose levels after eating different foods. We’d just been learning about how blood glucose could be lower in athletes due to higher muscle mass and increased insulin sensitivity. At the time, I was training for 20 hours a week. You can imagine my shock when I found that my results were close to the top end of the normal range. However, when I queried my doctor about this she assured me that it was still within the normal range. She told me that I needn’t be worried.

I’m going to explain to you why this is incorrect and why even slight changes in blood glucose can be a sign of insulin resistance. Studies have shown that up to 70% of women with PCOS have insulin resistance. I’m always amazed at the number of women I talk to who have been diagnosed with PCOS, but not tested for insulin resistance.

You were not born with PCOS. PCOS is a condition that develops due to your environment interacting with your genes. Your ‘environment’ includes what you eat, how much you exercise, stress levels, environmental toxins, etc. It’s therefore easy to see that there is always something in your environment causing your PCOS. If you can find out what this is then you can remove it, then reverse your PCOS symptoms.

I’ve written about the main causes of PCOS and how insulin resistance is the main one. Now I want to further explore insulin resistance:

  • What is it?
  • How is it impacting your PCOS?
  • How to find out if you have it?
  • Why ‘normal’ test results aren’t always normal

What Is Insulin Resistance?

Insulin is our storage hormone. When we eat, our body detects a rise in blood glucose. Brain, liver, pancreas, heart, and eye cells can all be damaged if blood glucose levels are continually elevated. Insulin is therefore used by our bodies to store excess glucose in our muscle and liver cells for later use.

Insulin is the hormone that tells the cells to open up and let the glucose in. Without it, our cells would starve. This is why Type 1 Diabetics (where the body doesn’t produce insulin), need to inject insulin to survive. Insulin is secreted by the pancreas and binds to a receptor on the cell to tell it to open up. This is similar to way a key opens a door. When the ‘key’ has been used too much (or there is chronic low grade inflammation), the lock starts to get a bit worn and clogged up. The ‘key’ no longer fits. This is insulin resistance.

How Does Insulin Resistance Cause PCOS?

The cells in our ovaries produce some of our essential hormones, including oestrogen and progesterone. These cells also secrete a small amount of testosterone. Testosterone is actually essential for many bodily functions, including libido and bone formation.

if you have really high insulin levels all the time then it causes your ovaries to overproduce testosterone. Our bodies usually have a system in place which prevents hormone levels from getting too high. Unfortunately this isn’t the case with testosterone and our bodies also don’t anticipate insulin making testosterone levels higher. As a result, there’s nothing to prevent testosterone levels spiraling out of control.

It doesn’t just end there though. When it comes to hormones, 80% should be bound to cells and 20% should be free in the body. The ‘free’ hormones are generally the ones which cause problems. Excess levels of ‘free’ testosterone can:

  • Get into hair follicles and make hair fall out.
  • Settle in hair follicles in our face and make it produce thick dark hair.
  • Get into skin glands and cause acne.

In most people, Sex Hormone Binding Globulin (SHBG) acts as a testosterone ‘sponge’, binding to excess testosterone and preventing it from causing these problems. However, insulin resistance reduces the amount of SHBG, thereby increasing testosterone levels.

You can think about insulin resistance as a delinquent child. He has put the plug in the bath, turned the testosterone taps on, stolen your sponges, and run away calling ‘catch me if you can!’

How Do Insulin Resistance and PCOS Affect Pregnancy?

The one thing you need to get pregnant is an egg that’s reached maturity and been released (ovulation). If your ovaries haven’t released any eggs then there is nothing to meet the sperm, stopping you from getting pregnant. Ovulation is controlled by a delicate balance of hormones.

After your period your body starts to prepare some baby eggs (follicles) to mature and be released. Contrary to popular belief, it’s actually many eggs (not one) so that the body has some backups. You can think of these eggs like Russian dolls. It’s not that they fit inside each other, but there are many of different sizes that are being prepared at different stages for ovulation. This part of the ovulation process is controlled by Follicle Stimulating Hormone (FSH). FSH stimulates the follicles to mature.

Once the biggest follicle is ready, it signals this to the body and Luteinizing Hormone (LH) is released. When Luteinizing Hormone reaches peak level, it will release the egg into the uterine tube. The egg is then ready for a conjugal visit from some awaiting sperm.

Anything that disrupts the processes of the egg’s maturity or release will stop ovulation. Scientists still don’t know exactly how insulin resistance and PCOS affects these processes. However, insulin has been shown to affect the following three things:

Insulin Affects the Delicate Hormone Balance

LH is like the switch for ovulation: you can only ovulate when your LH rises steeply. However, researchers think that the ratio of LH to FSH is the thing that’s really important for ovulation. Studies on PCOS have shown that insulin increases LH, damaging the LH:FSH ratio. Clomid is a drug which is given to many women with PCOS who are struggling to ovulate. Clomid increases FSH levels and re-balances the ratio.

Insulin Suppresses FSH

As I mentioned above, FSH’s role is to develop one of those ‘Russian Doll’ follicles into an egg. However, insulin resistance suppresses FSH. This means that all eggs are the same size and there isn’t a ‘superior’ one to be released into the uterine tube. These undeveloped follicles are what appear as ‘cysts’ on our ovaries.

Insulin Stops Follicles Developing Properly

High levels of insulin in the blood increase testosterone levels. Studies have shown that if follicles are exposed to too much testosterone when they are forming then they won’t develop properly. This is another way that too much insulin can impact pregnancy.

Why Do Some Women Have Insulin Resistance, But Not Develop PCOS?

Scientists still don’t know the answer to this question, but think that this is where genetics play a part. Studies have shown that there is a genetic component to PCOS and have identified which genes are most likely involved. These genes may make our ovaries and adrenal glands more sensitive to insulin and make them produce more androgens.

Having these genes doesn’t mean that you’re doomed. Studies have also shown that genes can be turned on and off by environmental factors. This is called epigenetics. We therefore need to remove these environmental factors to turn the PCOS genes off.

What Causes Insulin Resistance?

This is by no means an exhaustive list but here are some of the main causes of insulin resistance:

Inflammation (and Sugar)

You know how you’ve read (or may have been told by your doctor) that insulin resistance is caused by being lazy and eating too many sweets? Although these definitely contribute, eating too many refined carbohydrates isn’t the only cause.

Sugar is mostly to blame, but inflammation also plays a big part. Studies have now shown that inflammation can cause insulin resistance and may need to be present for insulin resistance to occur in the first place. Inflammation is a normal feature of our immune system and is critical for our survival. Problems arise when our immune system is chronically activated. This chronic inflammation damages our cells.

Women with PCOS have significantly higher levels of inflammatory blood markers than ‘normal’ women. It is also thought that PCOS is an inflammatory condition, like obesity, diabetes, heart disease, and cancer.

If you have insulin resistance and PCOS, then you almost certainly have inflammation. This is very important when considering PCOS treatment and is the reason why simply removing carbs isn’t effective for many women. Inflammation also needs to be treated.

For the purposes of this article, I’ll use the term ‘insulin resistance’, but you should read it as ‘inflammatory insulin resistance”.

The Birth Control Pill

Yes, the hormones that you’re given as a treatment for PCOS could actually be causing it. The pill that you’re given to ‘regulate your period’ can cause insulin resistance. A recent study of 42 women found that the pill caused inflammation and the beginnings of insulin resistance. This was after just 9 weeks of taking it.

As a side note, I wrote ‘regulate your period’ in inverted commas because the pill can never regulate your period. The pill causes a ‘pill bleed’, not a real period. A period is a withdrawal bleed from the hormones estradiol and progesterone (made by your ovaries). A pill bleed is a withdrawal bleed from pharmaceutical steroids, such as ethinylestradiol and levonorgestrel. The pill masks the problem and you still won’t have a regular period once you come off it.

Not Enough Sleep

Studies have shown that a lack of sleep can directly reduce insulin sensitivity. One study took two groups of men and put them in a hospital setting so they could control everything, from what they ate to how much they exercised. The amount of sleep that they had was the only thing that was manipulated.

When their sleep was reduced down to 5 hours a night, the men’s insulin sensitivity was reduced by 24%. This proves that you could be doing everything ‘right’ in regard to diet and exercise, but if you’re not sleeping enough then you are still going to be developing insulin sensitivity.

Imbalanced Gut Bacteria (Microbiome)

The microbiome is the name given to the bacteria, viruses, fungi, and protozoa that live throughout your body, specifically in your gut. It’s responsible for many different functions in the body, including 75% of our immune system. It is also directly responsible for how many calories and carbs we extract from our food.

This bacteria is completely normal, but problems arise when there is too much bad bacteria or not enough good bacteria. Too much bad bacteria causes too much insulin to be produced, leading to insulin resistance. Women with PCOS also have fewer good bacteria and more bad bacteria than normal.

What Tests Should I Get For Insulin Resistance and PCOS?

If you have PCOS, then there’s a up to a 70% chance that you have insulin resistance too. However, the only way to know for sure, and/or how severe your insulin resistance is, is by getting your insulin and glucose checked. You want to ask your doctor to perform the following tests:

  • Fasting blood glucose
  • Fasting insulin
  • HbA1c test(a measure of long term blood glucose)
  • Oral glucose tolerance test (or do your own testing with a glucometer).

What Do All These Insulin Resistance Tests Mean?

Fasting Blood Glucose

This is the most common test. It’s a measure of the concentration of glucose in the blood after an 8-12 hour fast. If results show that you have high levels of glucose in your blood then you likely have insulin resistance.

Fasting Insulin

This is similar to a fasting blood glucose test, but measures your insulin levels instead. Fasting insulin is one of the more accurate tests for insulin resistance. It shows when insulin is affected, which can often be well before glucose is.


An HbA1c test measures the amount of sugar stuck to your red blood cells. Sugar is sticky stuff, even inside your body. Red blood cells renew every three months, so the test supposedly provides an average blood sugar level from a three month period.

This is great in theory, but the test isn’t accurate if you have low iron levels. So although this is a great marker, it isn’t accurate on its own and needs to be combined with fasting insulin and fasting glucose.

Oral Glucose Tolerance Test

This test measures how well your blood glucose and insulin react to pure glucose. You’re given a glucose drink (that is very awful, I’m sorry!) and your blood glucose and insulin are measured. They should be measured fasting, before drinking the solution. Your blood glucose is then measured 1, 2, and sometimes 3 hours after drinking the solution. These levels are then used to plot a curve of the way your insulin is working, which is compared with an ‘ideal’ curve.

As you can see from the graphs below, your blood glucose and insulin levels should rise immediately after drinking the solution, but your insulin should be able to quickly clear the glucose from the blood and drop off quickly, so this is what the curve should look like.

If your insulin is struggling, it will be higher than normal at the 2 hour mark and your curve will look different.

insulin resistance and pcos

Similarly, your blood glucose will stay elevated for a much longer period of time in insulin resistance.

I never use just one of these tests on my patients, as they are just not accurate enough. I need all of them to give me the full picture. However, if I did have to chose just one, it would be the Oral Glucose Tolerance test, making sure that they measure insulin as well as glucose.

Why can’t I just get a fasting blood glucose test done?

Studies have shown that a fasting blood glucose test doesn’t pick up early stage insulin resistance. Insulin resistance develops over time. If you think about the lock and key analogy that I used earlier, in the early stages, insulin may be struggling to get the key into the lock as it’s become clogged up. But eventually insulin manages to force the key in and open it up, so glucose floods in, making your blood glucose appear normal. It’s not until the lock gets completely clogged up and insulin can no longer force the key in that blood glucose stays elevated for an extended period of time.

However, if we test insulin levels, we can see that it was struggling to open the lock, even in the early stages and insulin will be high on the test even when glucose is normal.
I’m sure that you’ll agree that it’s much better to catch this early and reverse it rather than letting it get completely out of control, so we ned to be using the best test possible.

What do I need to do to prepare for these tests?

  1. You will need to be fasted, which means that you would have blood taken in the morning before you eat and you’ve fasted for about 13 hours. So, for example, finish eating at 7pm the night before the test is taken at 8am the next morning.
  2. No exercise or stress, as they both cause your body to release glucose and will cause an incorrect reading.
  3. Eat a moderate amount of carbohydrates. It’s best if you eat a moderate to higher amount of carbs leading up to the tests, especially if you’ve been eating a low carb diet. If your body isn’t used to eating carbs, then it may overcompensate/ overproduce insulin, leading to a falsely elevated test result.

For the oral glucose tolerance test you will need to allow up to 4 hours, so take a good book with you to the clinic.

How Do You Know If Your Fasting Glucose or Insulin is ‘Normal’?

What’s considered normal (or what’s called the reference range) for people is defined at looking at a population without a disease then taking the average of that. So, for example, to get the current reference range for glucose, they asked thousands of people without insulin resistance if they could measure their blood glucose levels and created a bell shape curve out of that. If you fit in the 80th percentile, you’re normal.

But let’s critique that for a minute. Is that truly ‘normal’? Maybe it is—in the true definition of the word (although I would say common is a better word), but it doesn’t mean that it’s healthy. It merely means that you don’t have insulin resistance yet, but it doesn’t tell you anything about whether you’re on your way to developing it.

Doctors are also so busy with their large patient schedule that they don’t have time to look through your tests carefully. The laboratory will put an alert on the test to indicate if any of the tests were out of the normal range. So unless your doctor gets one of these alerts, they may not even look at the results and see that your results are borderline high.

In the UK and New Zealand, and possibly many other countries around the world, unless your blood tests are out of range, you don’t even get notified of the results. This means that you could be right on the cusp of the normal range and not know.

The medical normal range for fasting blood glucose is 3.61 to 6.0 mmol/L

You can be 6.0 and still be in the normal range. In fact, I had a patient who had exactly this happen to her.

I ask all my patients to provide me with their most recent tests so that I can get data to understand their root cause.

As you can see from the image below , her blood glucose was the very highest point of the medical ‘normal’ range at 6.0mmol/L and her HbA1c was also only one point away from being out of range.

However, she had never been notified of this or even sent the test results and so had no idea that she was so close to the upper limit, or what this even meant. Had I not asked for this patient’s results, she would have got a big shock in a year or so finding that she was on the fast track to Type 2 Diabetes.

What Should Your Blood Glucose Levels Actually Be?

In the functional medicine world, we don’t just take the average of non-diseased populations, we look for actually healthy people and find what their blood glucose is, and low and behold, this range is much smaller.

The functional medicine normal range is 4.16to 4.77!

As you can see, these ranges are quite different from the medical model. These are the ranges that I work with my clients to get into.

Don’t just accept being told that your levels are normal, or not being notified at all. If you get the actual figure, you can make an informed decision about how normal it actually is.

The second reason for this is that insulin resistance is not like catching a stomach bug, you don’t just wake up in the night with insulin resistance, it develops over time. By narrowing the normal range down to what’s actually healthy, we can catch those on their way to developing insulin resistance and stop it in its tracks.

What If My Doctor Won’t Approve These Insulin Resistance Tests?

From personal experience, I find that some doctors only want to test blood glucose and/or HbA1c, and if they’re normal then they won’t do the other tests. This could lead to you being missed for a few reasons:

  • Blood glucose is the last marker to be affected, even when insulin is struggling.
  • Your blood sugar could be ‘normal,’ but very, very close to the cut-off.
  • This is just a one-off blood reading, and therefore it could be abnormally high or low at that one point in time.
  • The medical ‘normal’ range is far to high.

You really need to have your insulin measured, and I would recommend that this be done with an Insulin assay- that’s an oral glucose tolerance test with insulin .

However, if your GP really refuses to approve these tests, you can opt to pay for them privately. I often order the glucose tolerance test for my patients, and as an indication, in the UK it is around £20 and in NZ about $40.