When did you last feel genuinely energized? Not temporarily stimulated by caffeine. Not running on adrenaline. Not forcing yourself through another afternoon because your calendar leaves you no other choice. When did you last wake up feeling restored, move through your day with steady energy, and still have something left for yourself by evening?
For many women over 40, that feeling has become difficult to remember.
Fatigue is often blamed on stress, poor sleep, work, family obligations, or simply getting older. Those factors can certainly contribute. But persistent exhaustion may also be connected to something happening much deeper inside the body: your cells may not have the nutrients or physiological support they need to produce energy effectively.
Meet Your Mitochondria
Mitochondria are structures inside your cells that convert nutrients and oxygen into ATP, the usable energy that powers nearly every function in your body. Your brain needs it to think clearly. Your muscles need it to move and recover. Your thyroid, liver, nervous system, immune system, and hormones all depend on healthy cellular energy production. But mitochondria cannot create energy from nothing. They require specific vitamins, minerals, amino acids, oxygen, and metabolic processes to work efficiently. When key nutrients are low—or when your body cannot properly absorb, convert, or use them—energy production may slow down.
The result can look like:
- Persistent physical fatigue
- Brain fog or slower thinking
- Poor exercise tolerance
- Weakness or heavy-feeling muscles
- Low motivation
- Mood changes
- Hair shedding
- Interrupted sleep
- Slow recovery
- Feeling exhausted despite “normal” test results
Here are several of the most important factors I evaluate when a patient tells me she is tired all the time.
1. Iron and Ferritin
Iron is essential for transporting oxygen throughout the body and supporting cellular energy production. Ferritin is a protein that stores iron and provides insight into the body’s iron reserves. A person can sometimes have a blood count that has not yet reached the threshold for anemia while still having low iron stores. That is one reason looking only at a basic blood count may not provide the full picture.
Low iron or ferritin may be associated with:
- Fatigue
- Weakness
- Reduced exercise tolerance
- Hair changes
- Restless or disrupted sleep
- Shortness of breath
- Headaches
- Difficulty concentrating
Women who experience heavy menstrual bleeding, digestive issues, restrictive diets, or impaired absorption may be especially vulnerable. Iron supplementation should not be started blindly. Both too little and too much iron can create problems, so testing and clinical guidance matter.
2. Magnesium
Magnesium participates in hundreds of reactions throughout the body, including processes involved in producing and using ATP. It also supports:
- Muscle and nerve function
- Blood sugar regulation
- Sleep
- Stress response
- Heart rhythm
- Bone health
- Recovery after exercise
Stress, certain medications, gastrointestinal problems, alcohol consumption, and inadequate dietary intake may all affect magnesium status. Some women take magnesium and still experience symptoms because the amount, form, absorption, or underlying cause of depletion has not been addressed.
3. Vitamin B12 and Folate
Vitamin B12 and folate work together in methylation, DNA synthesis, red blood cell formation, neurological health, and neurotransmitter production. Low B12 may contribute to physical fatigue, but many patients also describe cognitive and emotional symptoms, including:
- Brain fog
- Forgetfulness
- Slow mental processing
- Tingling or numbness
- Mood changes
- Reduced motivation
Folate is equally important, but the form of folate may matter. Some individuals have genetic variations that affect how efficiently their bodies process certain forms of folate.
This does not mean that everyone needs genetic testing or specialized supplements. It means that nutrient recommendations should be based on the individual—not a generic protocol found online.
4. Vitamin D
Vitamin D functions more like a hormone than a traditional vitamin. Its receptors are found throughout the body, and it plays a role in immune regulation, bone health, muscle function, mood, and other physiological processes. Low vitamin D may overlap with symptoms such as:
- Fatigue
- Low mood
- Muscle weakness
- Frequent illness
- Poor recovery
- Bone or joint discomfort
The appropriate vitamin D level and supplementation plan depend on the individual’s health history, existing level, diet, sun exposure, medications, and other factors. More is not always better. Vitamin D should be tested and monitored rather than taken indefinitely at high doses without guidance.
5. Zinc and Selenium
Zinc and selenium both contribute to healthy thyroid function.
The thyroid produces hormones that influence metabolism, body temperature, digestion, heart rate, mood, and energy. Selenium-dependent enzymes help convert thyroid hormone into its active form and protect thyroid tissue from oxidative stress.
Zinc also supports immune health, wound healing, reproductive health, and numerous enzymatic processes. Insufficient intake, digestive dysfunction, restrictive diets, and impaired absorption can all affect mineral status. Because thyroid symptoms and nutrient deficiency symptoms frequently overlap, a more complete evaluation may be needed to understand which factors are contributing.
6. Iodine
Iodine is a structural component of thyroid hormones. Without it, the thyroid cannot produce adequate amounts of T4 and T3.
Severe iodine deficiency is less common in the United States than it once was, but intake can vary significantly. People who avoid iodized salt, dairy, eggs, and seafood may consume less iodine than they realize.
However, iodine is another nutrient that should not be supplemented aggressively without context. Excessive iodine may also negatively affect thyroid function, particularly in individuals with certain thyroid conditions. The goal is not to assume deficiency. The goal is to evaluate the entire thyroid picture.
7. Protein
Protein is not a vitamin or mineral, but it is one of the most overlooked components of healthy energy and metabolism. Protein supplies amino acids that the body uses to:
- Preserve and build muscle
- Produce enzymes
- Create neurotransmitters
- Support immune function
- Repair tissue
- Maintain healthy blood sugar
- Support liver detoxification
- Produce hormones and signaling molecules
As women enter perimenopause and menopause, preserving muscle becomes increasingly important. Muscle supports strength, mobility, insulin sensitivity, metabolic health, and long-term independence. Many women dramatically underestimate how much protein they consume. Others eat most of their protein at dinner rather than distributing it throughout the day. A personalized nutrition plan should consider body size, activity level, kidney function, health goals, appetite, digestive health, and other medical factors.
Why Supplements May Not Fix the Problem
A supplement can provide a nutrient. It cannot automatically correct the reason that nutrient became depleted. Your body must be able to:
- Break down the food or supplement
- Absorb the nutrient through the digestive tract
- Transport it to the appropriate tissues
- Convert it into a usable form
- Deliver it inside the cell
- Use it within the correct metabolic pathway
Problems at any point in that process can affect the outcome.
For example, a person may be taking B12 but have difficulty absorbing it. Another may take iron without addressing ongoing blood loss. Someone else may take multiple thyroid-support supplements while an autoimmune condition, chronic stress pattern, or digestive issue remains unidentified. That is why the answer is rarely “take more supplements.” The better questions are:
- What is actually low?
- Why did it become low?
- Is the body absorbing it?
- Is the body converting it?
- Are medications interfering?
- Is inflammation affecting utilization?
- Is there continued loss or increased demand?
- Are hormones, thyroid function, or blood sugar contributing?
- Is the recommended form appropriate for this person?
“Normal” Does Not Always Answer the Entire Question
Laboratory reference ranges can help identify disease and significant abnormalities. But a result appearing inside a reference range does not automatically explain why a person feels unwell. Lab results should be interpreted alongside:
- Symptoms
- Medical history
- Menstrual history
- Diet
- Medications
- Supplements
- Digestive health
- Sleep patterns
- Stress physiology
- Hormone status
- Thyroid function
- Lifestyle and activity level
The objective is not to chase a perfect number. It is to understand patterns and connect those patterns with the person sitting in front of us.
Stop Guessing. Start Investigating.
Fatigue is common, but that does not mean it should be ignored. You are not lazy. You are not failing at self-care. And you are not automatically destined to feel exhausted because you are over 40. Your body may be asking for something it is not receiving—or struggling to use what you are already giving it.
At Ascent Health Center, we look beyond isolated symptoms to evaluate the interconnected factors that influence energy, hormones, thyroid function, metabolism, digestion, and overall health. A personalized evaluation may include a review of your symptoms, health history, nutrition, existing supplements, medications, and appropriate laboratory testing.
Ready to understand what may be draining your energy? Book an Appointment.