Inside: Fatigue that won’t lift isn’t “just getting older.” Learn what really drains women’s energy in their late 30s and 40s—and the key nutrients, habits, and tests that can help restore your spark.
My Own Story with Exhaustion
Although I was used to experiencing exhaustion from battling osteomyelitis (a jawbone infection) throughout my 20’s and early 30’s, when I hit my late 30’s exhaustion hit harder. I was eating well, moving daily, and sleeping well — yet I was waking every morning feeling like I’d run a marathon in my sleep. My head was foggy. I had little motivation. I could push myself through, but everything was more difficult than normal. Was it exhaustion from perimenopause I wondered?
Eventually, through a combination of gut, hormone and nutrient testing, I learned that it wasn’t just hormone-related fatigue. It was a combination of gut dysbiosis (imbalance of microorganisms in the gut), gluten intolerance, low vitamin D, low iron, poor detox function, and depleted mitochondria. I also learned I have the MTHFR and COMT genetic mutations, which meant I was not activating some B vitamins well. Just low B12 alone can cause brain fog, moodiness, and weakness [1].
But once I addressed those root causes — with improving my digestion, replenishing the right nutrients, and stress recovery — my energy slowly came back.
Why Exhaustion Can Hit Hard During Perimenopause
If you’re in your late 30’s or 40’s and feel as though your energy tank is permanently on empty, you’re not alone.
Perimenopause is when estrogen and progesterone start fluctuating, sometimes wildly. During times when estrogen surges, you may be wired but tired — having insomnia, tense muscles, racing thoughts. When it drops fatigue, low moods and brain fog move in. At this time, progesterone, your calming, sleep-supporting hormone, steadily declines. These shifts often affect your thyroid, adrenals, and blood sugar–all the systems regulating energy [4].
You may experience:
• Feeling wiped out after normal activity
• Requiring caffeine to function
• Crashing mid-afternoon
• Brain fog, forgetfulness or anxiety
• Unrefreshing sleep
• Heavier PMS fatigue or irritability
There is nothing wrong with you. It’s biology.
Common Causes of Exhaustion (Beyond Hormones)
Hormones are only part of the story. Many women in perimenopause also juggle jobs, families, and chronic stress–and that adds fuel to the fire. Common causes of exhaustion include chronic stress, poor sleep, under-eating or over-exercising without enough recovery or proper nutrition, sedentary habits, excessive sugar or alcohol intake, nutrient gaps (B12, iron, vitamin D, magnesium), gut issues, food sensitivities, environmental exposures, medications, and underlying medical conditions- such as thyroid or blood-sugar problems [3,5].
When your energy production pathways are running low on raw materials–vitamins, minerals, amino acids–your mitochondria (your cells’ “power plants”) will not be able to make enough ATP (energy to transfer). That’s what I mean by “something missing on the cellular level.”
Testing for Exhaustion–What to Get Checked
If you’ve been tired for months and still can’t find a clear cause, start with your doctor.
Ask for the following:
• Complete Blood Count (CBC) – check for anemia/infection
• Iron and Ferritin – important for transfer of oxygen
• Vitamin B12 and Folic Acid – low levels can mimic depression or brain fog [1,5]
• Vitamin D – important for hormones, mood, immunity
• Thyroid panel (TSH, Free T3, Free T4) – a sluggish thyroid is often missed [5]
• Blood Sugar or HbA1c – how handling glucose
• Urinalysis – screening for infection or stress on kidneys [5]
If everything looks “normal,” but you still feel awful – that is when functional testing can help reveal hidden culprits.
Functional Testing for Deeper Insight
As a Functional Nutritionist, I often use these advanced labs when a client’s fatigue doesn’t match their bloodwork:
- Organic Acid Testing (like the Metabolomix+ Test ⬇️ ): looks at energy production, detox pathways, neurotransmitter metabolites, and nutrient status — the cellular details standard labs leave out [2].
- Comprehensive Stool Testing: evaluates digestion, gut bacteria, inflammation, and markers tied to fatigue and nutrient absorption [5].
- Comprehensive Hormone Testing: maps cortisol rhythm and sex-hormone balance throughout the day and cycle [4].
These tests can uncover mitochondrial stress, evaluate nutrient depletion, unbalanced gut bacteria or issues with hormone rhythm, which can explain why you feel exhausted even when the basic labs are “fine.”
If you’re looking for more information specifically on gut testing, check out my post on stool testing kits and how they reveal the gut-energy link.
Metabolomix+ Test Reveal: The Missing Piece Behind Fatigue
Feeling drained, foggy, or stressed but your bloodwork says everything’s “normal”?
Discover how the Metabolomix+ test reveals what standard labs miss — from nutrient gaps and energy production to mood chemistry and detox balance.
👉 Learn how this test fits into my functional nutrition programs to uncover what’s really going on beneath the surface.
Why Exhaustion Feels Different in Perimenopause
During perimenopause, fluctuating hormones are changing how the body is using and storing energy. Low progesterone can make sleep lighter. Estrogen fluctuations can affect blood sugar and serotonin. Cortisol levels tend to be elevated due to stress and loss of sleep, which may suppress thyroid function. Putting all of this together, the energy system becomes sensitive so small missteps throughout the day (missing meals or staying out too late) hit harder than before [4,5].
This is why recovery is much more intentional at this time.
The Basics of Exhaustion Recovery
1. Eat a Balanced, Anti-Inflammatory Plate
- Build meals with protein + fiber + healthy fats to stabilize blood sugar.
- Load up on veggies for antioxidants and minerals.
- Have adrenal-friendly foods such as: avocado, almonds, citrus fruit, leafy greens, pumpkin seeds.
- Avoid missing meals or using caffeine to work through the day.
2. Replenish Key Nutrients
Support the systems that regulate energy:
- The B vitamins, vitamin C, and vitamin E for adrenal resilience [3,5]
- Magnesium to ease stress, relax muscles, and to sleep better [3]
- Vitamin D and zinc for immune balance and hormone balance [5]
- Selenium, iodine, and iron for thyroid function [5]
- CoQ10 and carnitine for mitochondrial energy [2]
If you haven’t yet, read my post on vitamin D deficiency — it’s one of the most common (and overlooked) contributors to fatigue. I go into some detail on symptoms, testing, and safe dosing of vitamin D in this post, so you can avoid the high dose hype.
3. Support Gut & Liver Function
Your gut and liver process hormones and other toxins, so keeping them strong impacts your energy.
- Eat garlic, artichokes, beans, cruciferous vegetables, dark leafy greens.
- Hydrate well.
- Reduce alcohol and ultra processed foods.
- Identify and reduce foods you are sensitive to.
4. Restore Your Circadian Rhythm
- Get morning sunlight within an hour of waking to re-set your internal clock.
- Keep caffeine before noon. Dim screens at night.
- Aim for 7-9 hours of sleep, and a consistent wind-down routine.
5. Manage Stress and Move Regularly
- Some gentle daily movement (walking, yoga, Pilates) helps keep cortisol balanced.
- Strength train twice a week to support your metabolism and muscle.
- Schedule rest–not just workouts and to dos. Your nervous system needs some downtime to rebuild energy.
Your Next Steps
If you have been caught in a cycle of fatigue, don’t ignore it. Your body is communicating it needs support.
Start with basic labs. Stabilize your meals and sleep. If the fatigue continues after this, that is your signal to dig deeper with functional testing. With the right nutrition, supplements targeted to your needs, and some support, you can regain energy–not overnight, but steadily, from the inside out.
Low energy, brain fog, or feeling run-down can be signs your iron needs support. This free guide and meal plan share simple, food-first ways to support iron absorption, steady your energy, and rebuild your iron levels naturally.
Final Thoughts
Exhaustion in perimenopause is not just a result of “getting older.” It is a signal that your body is asking for balance: hormonally, nutritionally, and emotionally. As you rebuild from the cellular level, your energy does not just return–it becomes more sustainable.
If you would like a gentle starting point, grab my free guide:
👉 5 Ways to Support Iron Levels Naturally — simple steps to support iron levels, calm your nervous system, and reduce the crashes that drain you. Check out all the free guides in the freebies library.
Ready for deeper support?
✨ The Calm & Clear Method — my 3-month program to uncover root causes of fatigue, hormone imbalance, and digestive distress through advanced testing and personalized nutrition.
You don’t have to live on empty. Let’s rebuild your energy from the inside out.
Be well,
Alysha Breanne
More Wellness Reads:
Alysha Breanne, CHN, CFNP — Certified Holistic and Functional Nutritionist helping women with iron deficiency, low ferritin, fatigue, and absorption issues restore steady energy using personalized nutrition and testing when needed.