Insulin

What It Is

Insulin is a metabolic hormone produced by the pancreas that regulates blood sugar (glucose) levels and controls how your body stores and uses energy. While insulin is not a sex hormone, it becomes profoundly relevant during perimenopause and menopause because estrogen decline disrupts insulin sensitivity, leading to metabolic changes that affect weight, energy, mood, and long-term health.

Where it's produced:

• Pancreas → specifically by beta cells in the islets of Langerhans

Primary functions:

• Regulates blood sugar → moves glucose from the bloodstream into cells (muscle, fat, liver) for energy or storage
• Supports energy storage → converts excess glucose to glycogen (stored in liver and muscle) or fat (stored in adipose tissue)
• Promotes fat storage → insulin signals the body to store energy, inhibiting fat breakdown
• Supports muscle building → insulin is anabolic (growth-promoting), helping muscles take up amino acids for repair and growth
• Regulates metabolism → affects how the body uses carbohydrates, fats, and proteins

How insulin works (the basics):

After you eat, carbohydrates are broken down into glucose (sugar), which enters the bloodstream. Rising blood sugar triggers the pancreas to release insulin.

Insulin acts like a key that unlocks cells, allowing glucose to enter and be used for energy. Once glucose is inside cells, blood sugar drops back to normal, and insulin levels decline.

When insulin works well (insulin sensitivity):

• Cells respond readily to insulin
• Blood sugar is efficiently regulated
• Energy is stable throughout the day
• Fat storage is balanced

When insulin doesn't work well (insulin resistance):

• Cells become less responsive to insulin → they "ignore" insulin's signal
• The pancreas produces more insulin to compensate → hyperinsulinemia (high insulin levels)
• Blood sugar remains elevated → over time, this can lead to prediabetes or type 2 diabetes
• Fat storage increases (especially abdominal fat)
• Energy, mood, and metabolism become dysregulated

Why It Matters During Perimenopause/Menopause

Insulin sensitivity often declines during perimenopause and menopause, and this shift has profound effects on weight, energy, metabolism, and long-term health.

Why insulin sensitivity declines:

1. Estrogen decline:

   • Estrogen enhances insulin sensitivity → estrogen helps cells respond to insulin
   • When estrogen declines, cells become less responsive to insulin → insulin resistance develops
   • This is why many women notice metabolic changes (weight gain, blood sugar issues) starting in perimenopause

2. Changes in body composition:

   • Muscle mass declines with age and estrogen loss → muscle is highly insulin-sensitive tissue, so less muscle = more insulin resistance
   • Fat mass increases (especially visceral fat—abdominal fat around organs) → visceral fat is metabolically active and worsens insulin resistance
   • Fat distribution shifts → estrogen loss causes fat to shift from hips/thighs (subcutaneous fat) to abdomen (visceral fat) → visceral fat is more insulin-resistant

3. Inflammation:

   • Estrogen has anti-inflammatory effects → when estrogen declines, inflammation increases
   • Chronic inflammation (from stress, poor diet, lack of sleep, visceral fat) → worsens insulin resistance

4. Stress and cortisol:

   • Chronic stress (common in perimenopause) → elevated cortisol
   • Cortisol raises blood sugar and promotes insulin resistance (cortisol is a "counter-regulatory" hormone that opposes insulin)
   • High cortisol + low estrogen = metabolic dysfunction

5. Sleep disruption:

   • Poor sleep (from night sweats, insomnia, stress) → worsens insulin resistance
   • Even one night of poor sleep can reduce insulin sensitivity by 20-30%

6. Aging:

   • Insulin sensitivity naturally declines with age (independent of menopause), but menopause accelerates the decline

The result:

Many women experience a perfect storm of metabolic changes during perimenopause:

• Declining estrogen → reduced insulin sensitivity
• Loss of muscle mass → less glucose disposal
• Increased visceral fat → more insulin resistance
• Chronic stress → elevated cortisol → higher blood sugar
• Sleep disruption → worsened insulin resistance

The vicious cycle:

• Insulin resistance → high insulin levels → increased fat storage (especially abdominal fat)
• Abdominal fat → more inflammation → worsened insulin resistance
• Worsened insulin resistance → higher insulin → more fat storage
• Repeat

Why this matters:

Insulin resistance affects far more than weight:

• Energy crashes → blood sugar swings create fatigue, brain fog, irritability
• Cravings → high insulin drives hunger, especially for carbs and sweets
• Mood and anxiety → blood sugar instability affects neurotransmitter function
• Long-term health risks → insulin resistance is the foundation of metabolic syndrome, which increases risk of type 2 diabetes, heart disease, stroke, Alzheimer's, and some cancers

Metabolic syndrome (a cluster of conditions that occur together):

• Insulin resistance and high blood sugar
• Abdominal obesity (waist circumference >35 inches for women)
• High triglycerides (blood fats)
• Low HDL cholesterol (the "good" cholesterol)
• High blood pressure

Metabolic syndrome is increasingly common during perimenopause and menopause, and it significantly increases the risk of cardiovascular disease and diabetes.

How It Works

Mechanism of action:

Insulin is released by the pancreas in response to rising blood sugar (after eating). It binds to insulin receptors on cells (especially muscle, fat, and liver cells), triggering a cascade of signals that:

1. Open glucose transporters (GLUT4) → allow glucose to enter cells
2. Activate glycogen synthesis → store glucose as glycogen in liver and muscle
3. Activate fat synthesis (lipogenesis) → store excess glucose as fat
4. Inhibit fat breakdown (lipolysis) → prevent stored fat from being released

When cells are insulin-sensitive:

• A small amount of insulin efficiently moves glucose into cells
• Blood sugar stays stable
• Energy is steady

When cells are insulin-resistant:

• Cells don't respond well to insulin → glucose stays in the bloodstream
• Pancreas produces more insulin to compensate → hyperinsulinemia (chronically high insulin levels)
• High insulin drives fat storage, hunger, inflammation, and further resistance

Insulin's relationship with other hormones:

Insulin + Estrogen:

• Estrogen enhances insulin sensitivity → helps cells respond to insulin
• Estrogen supports healthy fat distribution (hips/thighs vs. abdomen)
• When estrogen declines → insulin resistance increases, fat shifts to abdomen

Insulin + Cortisol:

• Cortisol raises blood sugar (releases stored glucose) → insulin must rise to bring it back down
• Chronic stress → chronic cortisol → chronic high blood sugar → insulin resistance
• High cortisol + high insulin → abdominal fat accumulation

Insulin + Testosterone:

• Insulin resistance can increase testosterone in women (via increased androgen production from ovaries and adrenals)
• This is the mechanism behind PCOS (polycystic ovary syndrome) → insulin resistance → high testosterone → irregular periods, acne, hair growth
• Some women entering perimenopause with insulin resistance may have PCOS-like symptoms

Insulin + Thyroid:

• Insulin resistance can worsen thyroid function (affects conversion of T4 to active T3)
• Hypothyroidism can worsen insulin resistance (metabolism slows, weight gain increases)
• Both affect energy, weight, metabolism—overlapping symptoms

Insulin + DHEA:

• DHEA supports insulin sensitivity
• Low DHEA (common in perimenopause) → worsened insulin resistance

Insulin + Leptin (satiety hormone) and Ghrelin (hunger hormone):

• High insulin → leptin resistance → brain doesn't "hear" satiety signals → overeating
• Insulin affects ghrelin (hunger hormone) → high insulin can increase hunger and cravings

What It Looks Like

When Optimal (Insulin Sensitivity)

Metabolic:

• Stable blood sugar throughout the day
• Healthy fasting glucose (70-99 mg/dL)
• Healthy fasting insulin (<10 μU/mL)
• Healthy HbA1c (<5.7%)
• Healthy body composition (balanced fat and muscle)

Energy:

• Steady energy (no crashes or spikes)
• No mid-afternoon energy slump
• Can go 4-5 hours between meals without hunger or irritability

Appetite:

• Normal hunger cues (hunger builds gradually, satisfied after meals)
• No intense cravings for carbs or sweets
• Comfortable eating smaller portions

Cognitive:

• Clear thinking, good focus
• Stable mood (no blood sugar-related irritability or anxiety)

Physical:

• Healthy weight or easy weight maintenance
• No abdominal bloating or puffiness after meals
• Good sleep quality

When Dysregulated (Insulin Resistance)

Metabolic:

• Elevated fasting blood sugar (100-125 mg/dL = prediabetes; ≥126 mg/dL = diabetes)
• Elevated fasting insulin (>10 μU/mL)
• Elevated HbA1c (5.7-6.4% = prediabetes; ≥6.5% = diabetes)
• Weight gain (especially abdominal, despite no change in diet/exercise)
• Difficulty losing weight (even with calorie restriction and exercise)

Energy:

• Energy crashes → especially after meals (blood sugar spike followed by crash)
• Mid-afternoon slump → need for caffeine or sugar to stay awake
• Fatigue despite adequate sleep
• "Hangry" → irritability, shakiness, brain fog if meals are delayed

Appetite:

• Constant hunger → never feel satisfied, even after large meals
• Intense cravings → especially for carbs, sweets, salty snacks
• Binge eating or overeating → driven by blood sugar dysregulation and leptin resistance

Cognitive:

• Brain fog → difficulty concentrating, slower thinking
• Memory problems → forgetfulness, "where did I put my keys?"
• Mood swings → irritability, anxiety (especially when blood sugar crashes)

Physical:

• Abdominal weight gain → "apple shape," increased waist circumference (>35 inches)
• Skin changes → skin tags (especially on neck, armpits), acanthosis nigricans (dark, velvety patches on neck, armpits, groin)
• Hair and skin issues → thinning hair, oily skin, acne (if testosterone is also elevated)
• Bloating, puffiness → water retention, inflammation

Reproductive (if still cycling):

• Irregular periods → insulin resistance can affect ovulation
• PCOS-like symptoms → high testosterone, acne, excess hair growth

Cardiovascular:

• High blood pressure (insulin resistance affects blood vessel function)
• High triglycerides, low HDL cholesterol (metabolic syndrome)
• Increased cardiovascular risk

Long-term risks:

• Type 2 diabetes
• Cardiovascular disease (heart attack, stroke)
• Non-alcoholic fatty liver disease (NAFLD)
• Alzheimer's disease (sometimes called "type 3 diabetes" due to insulin resistance in the brain)
• Some cancers (breast, endometrial, colon)

Phase Impact

Baseline (Regular Cycle, Pre-Perimenopause): Insulin sensitivity is generally healthy (assuming healthy lifestyle and no genetic predisposition). Estrogen supports insulin sensitivity. Muscle mass and body composition support healthy metabolism.

Electric Cougar (Early Perimenopause): Estrogen surges and crashes may cause blood sugar fluctuations. Stress (common in this phase) may elevate cortisol → worsen insulin sensitivity. Some women begin noticing weight gain (especially abdominal), energy crashes, or increased cravings.

Wild Tide (Mid-Perimenopause): Insulin resistance often becomes more apparent. Estrogen declines → reduced insulin sensitivity. Muscle mass begins to decline → worsened glucose disposal. Visceral fat increases → more insulin resistance. Many women notice significant metabolic changes: weight gain, energy crashes, cravings, difficulty losing weight.

Henapause (Late Perimenopause, 7-11 Months Without Period): Insulin resistance may worsen as estrogen continues to decline. Abdominal weight gain is common. Sleep disruption (night sweats, insomnia) worsens insulin sensitivity. Stress and cortisol elevation contribute to metabolic dysfunction.

The Pause (Menopause, 12+ Months Without Period): Insulin resistance stabilizes at a "new normal" (typically worse than pre-menopause unless actively addressed). Estrogen is consistently low → insulin sensitivity remains reduced. Body composition changes (less muscle, more fat) are established unless interventions are made.

Phoenix Phase (Early Post-Menopause, 2-10 Years After Last Period): Insulin resistance can improve with intentional lifestyle changes (strength training, low-carb eating, stress management). HRT (estrogen therapy) can improve insulin sensitivity. Women who prioritize metabolic health often report improved energy, weight, and well-being.

Golden Sovereignty (Established Post-Menopause, 7+ Years After Last Period): Insulin sensitivity and metabolic health depend heavily on lifestyle, HRT use, and overall health. Women who maintain muscle mass, manage stress, eat well, and stay active often maintain good insulin sensitivity. Those who don't may face increasing metabolic challenges (diabetes, cardiovascular disease, cognitive decline).

Testing & Optimization

When to Test

Insulin and blood sugar testing makes sense if you're experiencing:

• Weight gain (especially abdominal) despite healthy eating and exercise
• Energy crashes, especially after meals
• Constant hunger or intense cravings
• Difficulty losing weight
• Symptoms of metabolic syndrome (high blood pressure, abdominal obesity)
• Family history of diabetes or cardiovascular disease
• PCOS or PCOS-like symptoms

What tests measure:

Fasting glucose (blood test):

• Normal: 70-99 mg/dL
• Prediabetes: 100-125 mg/dL
• Diabetes: ≥126 mg/dL (on two separate tests)

Fasting insulin (blood test):

• Optimal: <10 μU/mL
• Insulin resistance: >10-15 μU/mL
• Note: Many doctors don't routinely test fasting insulin, but it's a valuable early marker of insulin resistance (often elevated years before blood sugar becomes abnormal)

HbA1c (glycated hemoglobin, blood test):

• Reflects average blood sugar over the past 3 months
• Normal: <5.7%
• Prediabetes: 5.7-6.4%
• Diabetes: ≥6.5%

HOMA-IR (Homeostatic Model Assessment of Insulin Resistance):

• Calculated from fasting glucose and fasting insulin
• HOMA-IR = (fasting glucose × fasting insulin) / 405
• <1.0 = optimal insulin sensitivity
• 1.0-2.9 = early insulin resistance

• 2.9 = significant insulin resistance

• Note: Not all doctors calculate this, but you can calculate it yourself if you have fasting glucose and insulin results

Oral glucose tolerance test (OGTT):

• Drink a glucose solution, then measure blood sugar (and sometimes insulin) at intervals (fasting, 1 hour, 2 hours)
• More sensitive than fasting glucose alone for detecting prediabetes or insulin resistance

Lipid panel (cholesterol, triglycerides):

• High triglycerides and low HDL cholesterol suggest insulin resistance and metabolic syndrome

Best timing for testing:

• Fasting (8-12 hours without food) for glucose, insulin, lipids
• Morning is best
• Avoid testing during acute illness or stress (can affect results)

Optimization Strategies

The good news: Insulin resistance is largely reversible with lifestyle changes. Even if you've developed prediabetes or metabolic syndrome, you can improve insulin sensitivity and reverse many of the metabolic changes.

1. Nutrition

Low-carb or low-glycemic eating:

• Reduce refined carbs and sugar → white bread, pasta, rice, sweets, sugary drinks
• Focus on whole foods → vegetables, lean protein, healthy fats, moderate whole grains (if tolerated)
• Low-glycemic carbs → foods that don't spike blood sugar (e.g., non-starchy vegetables, berries, legumes)
• Low-carb or keto → can be highly effective for reversing insulin resistance (especially in perimenopause/menopause)

Protein:

• Adequate protein (0.7-1.0 g per pound of body weight) → supports muscle mass, satiety, stable blood sugar
• Protein at every meal → prevents blood sugar spikes

Healthy fats:

• Omega-3s (fatty fish, flaxseeds, walnuts), olive oil, avocado, nuts, seeds
• Fat slows glucose absorption → more stable blood sugar

Fiber:

• Soluble fiber (vegetables, legumes, flaxseeds, chia seeds) → slows glucose absorption, supports gut health, improves insulin sensitivity

Intermittent fasting:

• Time-restricted eating (e.g., 16:8—fast for 16 hours, eat during an 8-hour window)
• Fasting periods give insulin a chance to drop → improves insulin sensitivity
• Not for everyone (especially if history of disordered eating), but many women find it helpful during menopause

Avoid:

• Sugary drinks (soda, juice, sweetened coffee drinks)
• Processed foods, refined carbs
• Excessive alcohol (raises blood sugar, worsens insulin resistance)

2. Exercise

Strength training (resistance training):

• Most important for insulin sensitivity
• Muscle is highly insulin-sensitive → more muscle = better glucose disposal
• Strength training builds muscle, improves insulin sensitivity, reduces visceral fat
• Aim for 2-4 sessions per week (full-body or split routine)

Cardiovascular exercise:

• Walking, jogging, cycling, swimming, dancing
• Improves insulin sensitivity, supports cardiovascular health, reduces stress
• Aim for 150+ minutes per week (or 30 minutes most days)

Post-meal walks:

• Even a 10-15 minute walk after meals can significantly reduce blood sugar spikes
• Muscles take up glucose without needing insulin (exercise activates GLUT4 transporters independent of insulin)

High-intensity interval training (HIIT):

• Short bursts of intense exercise → improves insulin sensitivity, burns fat, builds muscle
• Not for everyone (requires good fitness base), but highly effective

3. Stress Management

Chronic stress → high cortisol → insulin resistance:

• Prioritize stress reduction: meditation, breathwork, therapy, boundaries, time in nature
• Nervous system regulation: vagal toning, somatic practices, yoga
• Sleep (see below)

4. Sleep

Poor sleep worsens insulin resistance:

• Prioritize 7-9 hours of quality sleep
• Sleep hygiene: cool, dark room, consistent schedule, limit caffeine/alcohol, manage night sweats
• Address sleep disorders (sleep apnea, insomnia) with medical support

5. Supplements

Evidence-based supplements for insulin sensitivity:

• Berberine → plant compound that improves insulin sensitivity (comparable to metformin in some studies); typical dose 500 mg 2-3x/day
• Inositol (myo-inositol + D-chiro-inositol) → improves insulin sensitivity, especially in PCOS; typical dose 2-4 g/day
• Magnesium → supports insulin function; deficiency worsens insulin resistance; typical dose 300-400 mg/day
• Chromium → supports glucose metabolism; typical dose 200-400 mcg/day
• Alpha-lipoic acid → antioxidant that improves insulin sensitivity; typical dose 300-600 mg/day
• Omega-3 fatty acids → reduces inflammation, improves insulin sensitivity; typical dose 1-2 g/day

Note: Supplements are not a substitute for diet and exercise, but they can provide additional support. Discuss with clinician, especially if on diabetes medications.

6. Medications

Metformin:

• First-line medication for prediabetes and type 2 diabetes
• Improves insulin sensitivity, reduces glucose production by the liver
• Can support weight loss
• Generally well-tolerated (main side effect: GI upset, which usually improves)
• Some functional medicine doctors prescribe metformin for insulin resistance even without diabetes

GLP-1 agonists (semaglutide/Ozempic/Wegovy, tirzepatide/Mounjaro/Zepbound):

• Newer class of medications that improve insulin sensitivity, support weight loss
• Highly effective for weight loss and metabolic health
• Require injection (weekly or daily, depending on medication)
• Expensive; insurance coverage varies

SGLT-2 inhibitors:

• Medications that cause kidneys to excrete excess glucose
• Support weight loss, improve insulin sensitivity, reduce cardiovascular risk

HRT (Hormone Replacement Therapy):

• Estrogen therapy improves insulin sensitivity → restores some of the metabolic benefits of estrogen
• Women on HRT often have better metabolic profiles than those not on HRT
• Discuss with clinician if metabolic changes are a concern

When to Review with Clinician

You should discuss blood sugar and insulin testing if:

• Weight gain (especially abdominal) despite healthy eating and exercise
• Energy crashes, constant hunger, intense cravings
• Difficulty losing weight
• Family history of diabetes or cardiovascular disease
• Elevated blood pressure or cholesterol
• Symptoms of metabolic syndrome (abdominal obesity, high triglycerides, low HDL, high blood pressure)
• PCOS or PCOS-like symptoms (irregular periods, acne, excess hair growth)
• Skin changes (skin tags, dark patches on neck or armpits)

Red flags requiring immediate medical attention:

• Very high blood sugar (>300 mg/dL) → risk of diabetic ketoacidosis or hyperosmolar hyperglycemic state
• Symptoms of diabetes: excessive thirst, frequent urination, unexplained weight loss, blurred vision, slow-healing wounds
• Chest pain, shortness of breath (possible cardiovascular event)

Work with a knowledgeable clinician:

• Endocrinologist (hormone specialist)
• Integrative or functional medicine doctor (often more proactive about preventing diabetes)
• Registered dietitian (for nutrition support)

Related Terms

• estrogen
• cortisol
• metabolic-syndrome
• insulin-resistance
• prediabetes
• type-2-diabetes
• weight-gain
• visceral-fat
• energy-crashes
• cravings
• hrt-hormone-replacement-therapy
• strength-training