Insulin

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What is insulin?
Where is insulin produced?
Function of insulin
Insulin resistance
Insulin and fertility
Normal insulin levels
Causes of high insulin
Causes of low insulin
When and how to test insulin
Insulin in traditional Chinese medicine
Acupuncture and insulin
Chinese herbal medicine and insulin
Diet, supplements and lifestyle
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1. What is insulin?

Insulin is a peptide hormone produced by the beta cells of the pancreas. Its primary role is to regulate blood glucose by allowing glucose to enter cells and by promoting the storage of glucose, fat and protein. Although not traditionally thought of as a fertility hormone, insulin has profound effects on fertility — particularly in women with PCOS, where insulin resistance is the underlying driver of the condition.

Reference ranges vary from country to country and between laboratories. Always interpret your own result against the reference range provided by the laboratory that performed your test.

2. Where is insulin produced?

Insulin is produced exclusively by the beta cells of the pancreatic islets of Langerhans. It is released in response to rising blood glucose, particularly after meals containing carbohydrates. The pancreas releases small amounts of insulin continuously (basal secretion) plus larger pulses after eating (postprandial secretion).

3. Function of insulin

The main functions of insulin are:

Allowing glucose to enter cells, particularly muscle and liver.
Promoting the conversion of glucose into glycogen for storage in the liver and muscle.
Stimulating the synthesis of fatty acids and storage of fat.
Stimulating protein synthesis.
Suppressing the breakdown of stored fat and glycogen.
Reducing SHBG production by the liver, increasing free testosterone.
Stimulating ovarian theca cells to produce androgens.

4. Insulin resistance

Insulin resistance is a state in which body tissues respond poorly to insulin. The pancreas compensates by producing more insulin, leading to high circulating insulin (hyperinsulinaemia) with normal or only slightly raised blood glucose. Over time, the pancreas may fail to keep up, blood glucose rises and type 2 diabetes develops.

Insulin resistance is the central feature of PCOS in approximately 70% of women with the condition, and is closely associated with central obesity, polycystic ovaries, irregular cycles, anovulation, hirsutism and infertility. Importantly, lean women with PCOS can also have insulin resistance.

5. Insulin and fertility

High insulin affects fertility through several mechanisms:

Reduces SHBG — increasing free testosterone, which contributes to PCOS.
Stimulates ovarian theca cells — directly increasing androgen production.
Disrupts the LH:FSH ratio — increasing LH relative to FSH.
Impairs follicle development — multiple immature follicles instead of one dominant follicle.
Affects egg quality through advanced glycation end-products (AGEs) and oxidative stress.
Affects implantation through AGE-mediated damage to the uterine lining.

Low insulin (as in type 1 diabetes or severe undereating) reduces stimulation of the pituitary and ovaries, causing irregular menstrual cycles and infertility.

6. Normal insulin levels

Typical reference ranges:

Fasting insulin: 2.6–24.9 mIU/L (or pmol/L), but for fertility a fasting insulin below 10 mIU/L is preferable.
Fasting glucose: <5.5 mmol/L (<100 mg/dL).
HbA1c: <42 mmol/mol (<6.0%).
HOMA-IR (insulin resistance score): <1.5 is optimal; >2.5 indicates insulin resistance.

Reference ranges vary from country to country and between laboratories.

7. Causes of high insulin

High insulin is caused by:

Insulin resistance — the most common cause.
Excess body weight — particularly central obesity.
Diet high in refined sugar and refined carbohydrates.
Sedentary lifestyle.
Chronic stress — cortisol drives insulin resistance.
PCOS.
Some medications — including corticosteroids and some antipsychotics.
Genetic factors.

8. Causes of low insulin

Low insulin is seen in:

Type 1 diabetes — autoimmune destruction of pancreatic beta cells.
Severe pancreatitis or pancreatectomy.
Severe undereating, anorexia or fasting.
Late stage type 2 diabetes — when the pancreas eventually fails.

9. When and how to test insulin

Insulin is best measured fasting alongside fasting glucose, allowing the calculation of the HOMA-IR insulin resistance score. A 2-hour oral glucose tolerance test (OGTT) with simultaneous insulin measurements gives a fuller picture and can detect early insulin resistance that fasting tests miss. HbA1c is a useful additional marker reflecting average glucose control over the past three months.

Reference ranges vary from country to country. Always interpret your own result against the laboratory's reference range and discuss it with your doctor or fertility specialist.

10. Insulin in traditional Chinese medicine

In traditional Chinese medicine, the pancreas is part of the Spleen organ system. Insulin resistance most commonly reflects a pattern of Spleen Qi deficiency with Damp-Phlegm accumulation, often combined with Liver Qi stagnation from chronic stress. The classic picture of central obesity, fatigue, sweet cravings and a thick tongue coating fits this pattern very precisely.

11. Acupuncture and insulin

Research has shown that acupuncture can improve insulin sensitivity, reduce fasting insulin and improve glucose control in women with PCOS. The mechanisms include reducing cortisol, improving autonomic nervous system balance, and direct effects on muscle insulin signalling. Acupuncture is most effective when combined with dietary and lifestyle changes.

12. Chinese herbal medicine and insulin

For insulin resistance with Damp-Phlegm pattern, Cang Fu Dao Tan Tang is a commonly used formula. Bai Zhu, Cang Zhu, Fu Ling, Chen Pi, Ban Xia and Huang Lian are widely used herbs. Where Liver Qi stagnation is also present, Xiao Yao San is added.

13. Diet, supplements and lifestyle

To improve insulin sensitivity:

Cut out refined sugar and reduce refined carbohydrates (white bread, white rice, pastries).
Eat protein and healthy fats with every meal to slow glucose absorption.
Eat plenty of high-fibre vegetables.
Exercise regularly — particularly resistance training and high-intensity interval training (HIIT).
Take myo-inositol (250–500 mg daily, sometimes higher with d-chiro-inositol) — research has shown benefits in PCOS comparable to or better than metformin without the side effects.
Other useful supplements include chromium, alpha lipoic acid, magnesium and vitamin D.
Sleep before 10 p.m. and aim for seven to eight hours per night.
Reduce psychological stress.
Avoid artificial sweeteners — research has shown they can disrupt insulin signalling.