7 minute read

In this article:

• Type 1: Stress and HPA axis fatigue
• Type 2: Mitochondrial and cellular energy fatigue
• Type 3: Iron and ferritin deficiency fatigue
• Type 4: Thyroid-related fatigue
• Type 5: Blood sugar dysregulation fatigue
• Type 6: Nutritional depletion fatigue
• How do you know which type you have?
• What nutritional support can do

Low energy is a health complaint I hear more than any other in clinical practice, and as a practitioner I know that I'm not alone. It is one of the most complained about symptoms in the UK. When you look at the various causes of low energy, this isn't surprising, and it also explains why it can be so hard to get on top of.

It is often treated as a single problem with a single solution, when in reality it is often several different problems that happen to share the same name.

Before I make any recommendations to my clients to address their energy, I'm always sure to ask which type of fatigue they actually have first, because this gives clues as to the underlying issues going on.

Why fatigue can be tricky to get on top of

Low energy covers a huge amount of physiological ground. Fatigue driven by iron deficiency looks and feels different to fatigue driven by chronic stress. Mitochondrial dysfunction produces a different pattern to blood sugar dysregulation. Thyroid-related fatigue has its own distinct signature. Yet in a ten-minute GP appointment, many of these can overlap and sometimes result in the same outcome: being told your bloods are 'normal' and your tiredness is probably stress.

In my clinic, I never approach fatigue as one thing but rather as a question. And the answer (when you find it) strongly helps inform what comes next.

Here are the six types I see most often in women, and what to do about them, so you can help lift that lingering fog for good.

Type 1: Stress and HPA axis fatigue

The HPA axis (the hypothalamic-pituitary-adrenal axis) is the body's central stress-response system. When we experience stress, the brain signals the adrenal glands to release cortisol. In the short term this is appropriate. The problem arises when stress is sustained over months or years, as it so often is for women in their 30s, 40s, and beyond.

Chronically elevated cortisol can begin to dysregulate the normal cortisol rhythm - the pattern of higher cortisol in the morning that gives us drive and energy, falling gently through the day. When this rhythm is disrupted, women often describe a very particular pattern: wired but exhausted in the evening, unable to wind down, then flat and unrestorable in the morning despite adequate sleep hours. They may also wake up in the night and be unable to fall back asleep. The classic description is "tired but wired."

Over time, sustained HPA axis activation also depletes the nutrients required for cortisol production - particularly B vitamins, magnesium, and vitamin C - compounding the energy deficit further. I want to add here that this isn't about the loosely termed 'adrenal fatigue' or adrenal exhaustion, instead about supporting healthy adrenal function to keep you feeling resilient, balanced and on an even keel.

What helps:

Lifestyle

Morning daylight exposure within 30 minutes of waking is one of the most evidence-backed ways to reset the cortisol rhythm - natural light signals the suprachiasmatic nucleus to anchor the cortisol peak at the right time of day, which has a downstream effect on energy, mood, and sleep quality. In the evening, reducing light exposure after 6pm - particularly blue light from screens - supports the natural cortisol decline and allows melatonin to rise at the right time. Slowing down after 6pm is not a luxury; for women with disrupted cortisol rhythms it is physiologically necessary. Eating your last meal at least two hours before bed (ideally before 8pm) allows digestion to complete before the body shifts into repair and recovery mode, and reduces the cortisol spike that late eating can trigger.

Diet

Magnesium-rich foods - chard, kale, spinach, pumpkin seeds, dark chocolate, avocado, and legumes support the GABA system and cortisol regulation. B vitamin-rich foods including eggs, oily fish, meat, legumes, and whole grains help replenish the nutrients most depleted by the stress response. Caffeine deserves specific mention: it directly stimulates cortisol release, which compounds HPA axis dysregulation in women who are already running high. Limiting caffeine to two cups per day with the last one before midday allows cortisol to follow its natural declining curve through the afternoon and evening, and significantly improves sleep architecture over time.

Supplements

Adaptogenic support is the most well-evidenced nutritional intervention here. KSM-66 ashwagandha has been studied extensively for its effects on cortisol and stress perception. A 2019 randomised double-blind placebo-controlled trial in 60 adults found that ashwagandha supplementation significantly reduced stress and anxiety scores, and improved sleep quality compared to placebo.¹ Siberian ginseng, included in our new Energy Formula, has similarly demonstrated support for physical and mental performance under stress.² Magnesium bisglycinate and active B vitamins replenish the nutrients most depleted by the stress response.

Type 2: Mitochondrial and cellular energy fatigue

Mitochondria are the energy-producing structures within every cell. These generate ATP, the molecule that powers virtually every biological process in the body. When mitochondrial function declines (through chronic stress, poor diet, environmental toxins, ageing, or nutrient deficiency) cells produce less ATP and the body runs on a reduced energy budget.

This type of fatigue tends to feel heavy and pervasive. It is not the sharp, wired exhaustion of HPA axis fatigue but something flatter - a sustained depletion of drive and physical energy that does not respond to caffeine or willpower.

Mitochondrial decline is increasingly understood as a central feature of biological ageing, but it is also something that can be influenced meaningfully through nutrition and lifestyle. CoQ10 is one of the most critical nutrients for mitochondrial energy production. It sits within the electron transport chain and is essential for ATP synthesis. Levels decline naturally with age, and supplementation has been shown to improve energy markers and reduce fatigue in clinical populations.³

Lifestyle

Regular movement (even gentle daily walking) stimulates mitochondrial biogenesis, the process by which the body generates new mitochondria. Resistance exercise is also particularly effective. Chronic sedentary behaviour, by contrast, accelerates mitochondrial decline. Sleep is non-negotiable: the majority of mitochondrial repair occurs during deep sleep, and consistently poor sleep compounds mitochondrial dysfunction. Reducing alcohol intake is also meaningful here — alcohol directly impairs mitochondrial electron transport chain function and is one of the most underappreciated contributors to this type of fatigue.

Diet

A diet rich in antioxidants from colourful vegetables and fruit helps protect mitochondria from the oxidative stress that accumulates with age and chronic stress. Particularly useful foods include blueberries, dark leafy greens, cruciferous vegetables, turmeric and oily fish. Adequate protein (around 1g per kg of body weight daily) provides the amino acids required for mitochondrial repair and biogenesis. Reducing ultra-processed foods, which are high in inflammatory seed oils and additives that directly impair mitochondrial function, is one of the most impactful dietary changes for this fatigue type.

Supplements

CoQ10 is one of the most critical nutrients for mitochondrial energy production because it sits within the electron transport chain and is essential for ATP synthesis. Levels decline naturally with age, and supplementation has been shown to improve energy markers and reduce fatigue in clinical populations³ which is why we added this to Energy Formula. Cordyceps extract, also included in Energy Formula, has demonstrated promising effects on cellular oxygen utilisation and energy metabolism in human studies. A randomised controlled trial found that three weeks of supplementation with a cordyceps-containing mushroom blend significantly improved VO₂ max and exercise tolerance compared to placebo - with greater benefits observed with consistent supplementation over time.⁴ B vitamins in their active forms (particularly B1, B2, B3, and B5) directly fuel the mitochondrial energy pathway.

Type 3: Iron and ferritin deficiency fatigue

Iron deficiency is the most common nutritional deficiency in women globally. Low iron or anaemia is easy to spot on a blood test (that's if you manage to get one) but it's also worth noting that low ferritin can sometimes be missed.

Ferritin is the body's iron storage protein, and a result within the normal laboratory range (which in the UK can be as low as 15 ng/mL) is frequently interpreted as adequate. But research consistently shows that fatigue, cognitive impairment, and reduced physical performance can occur at ferritin levels well within the so-called normal range. Low ferritin is more common in women who have monthly periods, are pregnant (or have recently given birth) or who have heavy periods. Poor digestion can also be a factor here, as it impacts iron absorption.

A randomised double-blind placebo-controlled trial in 90 non-anaemic premenopausal women with low ferritin found that iron treatment significantly reduced fatigue scores compared to placebo — with the strongest effects seen in those with ferritin levels at or below 15 ng/mL.⁵ Many integrative practitioners now aim for ferritin levels of at more like 50 ng/mL in women experiencing fatigue, rather than accepting low-normal results as sufficient.

This type of fatigue tends to manifest as a physical heaviness, feeling tired 'to your bones', particularly on exertion, alongside poor concentration, pallor, and sometimes hair loss — which appears several months later as iron stores fall. Some people can also complain of heart racing when walking up the stairs when they have iron deficiency anaemia.

Lifestyle

Avoiding tea and coffee within an hour of meals significantly improves dietary iron absorption - the tannins in both can reduce iron uptake by up to 60%. This is one of the simplest and most impactful lifestyle changes for women with low ferritin. Cooking in cast iron pans particularly with acidic foods like tomatoes, can meaningfully increase the iron content of meals. Reducing high-intensity exercise temporarily may also be warranted in cases of significant iron deficiency, as intense training accelerates iron losses through haemolysis.

Diet

Haem iron from red meat, lamb, and dark poultry is the most bioavailable form of dietary iron and is absorbed at a rate approximately three times higher than non-haem iron from plant sources. For women who eat meat, including red meat two to three times per week is one of the most effective dietary strategies for raising ferritin. For plant-based women, pairing non-haem iron sources — lentils, tofu, pumpkin seeds, spinach, fortified foods — with vitamin C at the same meal significantly enhances absorption. Vitamin C converts non-haem iron to a more absorbable form, and the effect is substantial. It's also vital to keep on top of B12, folate and other B vitamins, since these all work together to create healthy red blood cells.

Supplements

When iron supplementation is warranted, the form matters enormously. Ferrous sulphate (the standard prescription form) is associated with significant gastrointestinal side effects including nausea, constipation, and cramping, which are the most common reasons women stop taking it before their stores recover. Ferrochel®, the form of iron bisglycinate used in Energy Formula, is a chelated iron where the molecule is bound to glycine, which protects it from competitive inhibition in the gut and allows absorption through a different intestinal pathway to conventional iron salts. A randomised comparative trial found that iron bisglycinate produced equivalent or superior increases in ferritin compared to ferrous sulphate, with significantly fewer side effects and better tolerability.⁶

The dose in Energy Formula (7mg per serving) is intentionally gentle. It is designed to support iron status daily over time, not as a high-dose therapeutic correction and this also means that women with normal iron status are not at risk of overload.

Type 4: Thyroid-related fatigue

The thyroid gland regulates the metabolic rate of virtually every cell in the body. When thyroid output is suboptimal, including at the subclinical level where TSH is elevated but still within the reference range, energy production slows throughout every organ and tissue simultaneously.

Thyroid-related fatigue tends to be accompanied by other characteristic signs: weight gain or difficulty losing weight, sensitivity to cold, constipation, dry skin or hair, brain fog, and low mood. Hair loss, particularly diffuse thinning across the scalp, is common. Many of these symptoms overlap significantly with perimenopause, which means thyroid dysfunction is frequently missed in women in their 40s because symptoms are attributed to hormonal change rather than investigated properly.

If thyroid-related fatigue is suspected, a full thyroid panel - TSH, free T3, free T4, and thyroid antibodies — is the right first step. Nutritional support has a role, but undiagnosed hypothyroidism requires medical assessment.

Lifestyle

Managing stress is directly relevant to thyroid function - chronic cortisol elevation suppresses thyroid stimulating hormone (TSH) and impairs the conversion of T4 to active T3. Cruciferous vegetables, often cited as problematic for thyroid function due to goitrogenic compounds, are generally safe when consumed cooked and in normal dietary quantities and do not need to be avoided.

Diet

Brazil nuts are one of the richest dietary sources of selenium, and just two to three per day provide an optimal selenium dose to support T4 to T3 conversion. Seaweed and seafood provide dietary iodine. Eggs, dairy, and meat provide both iodine and selenium alongside zinc and iron, all of which support thyroid function. Avoiding severely restrictive diets is important because very low-calorie intake suppresses thyroid output as a survival mechanism, compounding thyroid-related fatigue.

Supplements

Thyroid function is supported nutritionally by iodine (found in Energy Formula as kelp), selenium, zinc, and iron - the latter three being essential cofactors for the conversion of inactive T4 to active T3. Tyrosine is also important, as is iron – both included in our Energy Formula.

Type 5: Blood sugar dysregulation fatigue

The rollercoaster pattern of energy is something I hear about often in clinic. It can sound like feeling good after meals, then crashing mid-morning or mid-afternoon, needing sugar or caffeine to get through the day. This is one of the most common fatigue presentations I see, and many women don't even realise they are in it as appetite isn't always impacted, especially for those relying on coffee to pull through.

When blood sugar spikes rapidly, say after refined carbohydrates, sugar, alcohol, or a meal lacking sufficient protein and fat, insulin rises to bring it back down. For some women, this correction can be sharper than the body would like, producing an energy dip that triggers cortisol and adrenaline to stabilise blood glucose again. Not everyone experiences this dramatically, and individual responses vary considerably - but the pattern of repeated blood sugar fluctuation throughout the day is tiring for anyone, regardless of how pronounced the swings are.

The broader eating pattern matters too - frequent snacking on refined foods, skipping proper meals, or eating a diet consistently high in processed carbohydrates keeps insulin elevated across much of the day, creating a background state of metabolic busyness that drains energy and places an ongoing demand on the adrenal glands. Over time this compounds the HPA axis dysregulation described in type 1 - the two patterns frequently appear together and reinforce each other.

Lifestyle

A ten-minute walk after meals is one of the most evidence-backed interventions for blunting the post-meal glucose spike because it activates glucose uptake by muscle cells independently of insulin, reducing the peak and the subsequent crash. Avoiding eating late at night (particularly high-carbohydrate meals) supports overnight blood sugar stability and reduces the likelihood of the 3am cortisol spike that wakes many women with blood sugar dysregulation.

Diet

Every meal should contain protein, fat, and fibre alongside any carbohydrates. This is not about avoiding carbohydrates - it is about slowing their digestion and absorption so that glucose enters the bloodstream gradually rather than in a rush. Breakfast deserves particular attention: starting the day with a protein and fat-forward meal - eggs, feta, smoked salmon, full-fat yoghurt, nuts - rather than refined carbohydrates or fruit juice sets the blood sugar tone for the entire day. Vinegar (a tablespoon of apple cider vinegar in water before meals) has been shown in small trials to reduce post-meal glucose responses, though it is not essential.

Supplements

Chromium has demonstrated blood sugar regulatory effects and is included in Energy Formula alongside magnesium bisglycinate, which supports insulin sensitivity. Both nutrients are commonly depleted in women consuming diets high in refined carbohydrates and sugar, which itself worsens the underlying pattern.

Type 6: Nutritional depletion fatigue

This is the fatigue that accumulates quietly over years of demanding life stages — pregnancy, postpartum, heavy menstrual cycles, periods of poor diet, high stress, and little sleep. The body can compensate for nutritional shortfalls for a significant period before the deficit becomes symptomatic, which is why this type of fatigue often appears to come from nowhere.

B vitamins are the most critical nutrient group here. They sit at the heart of cellular energy production - B1, B2, B3, and B5 are all directly involved in the mitochondrial pathway that converts food into ATP. B6, B12, and folate drive methylation, the biochemical process underpinning mood, hormonal clearance, and neurological function. Active, methylated forms (pyridoxal-5-phosphate (B6), methylcobalamin (B12), and 5-methyltetrahydrofolate (folate)) are significantly more bioavailable than standard forms and are what the body actually uses and in my clinic I find these to be incredibly helpful for those suffering with fatigue.

Magnesium is involved in over 300 enzymatic reactions, including many central to energy metabolism. Deficiency is common in women under sustained stress and is associated with fatigue, poor sleep, muscle tension, and low mood.

Lifestyle

Prioritising sleep above almost everything else is the most important lifestyle intervention for this type of fatigue because growth hormone secreted during deep sleep is the primary driver of cellular repair and nutrient utilisation. Reducing alcohol is also significant here: alcohol directly depletes B vitamins, folate, magnesium, and zinc.

Diet

Shoot for a diverse, whole-food diet is the foundation. The goal is nutritional breadth rather than perfection - eating a wide variety of vegetables, proteins, whole grains, legumes, nuts, seeds, and oily fish provides the full spectrum of micronutrients that energy pathways depend on. Specific foods worth prioritising for this fatigue type include eggs (B12, choline, selenium), dark leafy greens (folate, magnesium, iron), oily fish (B12, omega-3, vitamin D), legumes (B vitamins, iron, magnesium), and pumpkin seeds (zinc, magnesium, iron). Eating regularly and not skipping meals matters - energy pathways cannot run efficiently on an intermittent fuel supply.

Supplements

B vitamins are the most critical nutrient group for this fatigue type — B1, B2, B3, and B5 directly fuel the mitochondrial energy pathway; B6, B12, and methylfolate drive methylation underpinning mood, hormonal clearance, and neurological function. Active methylated forms are significantly more bioavailable than standard forms. Magnesium bisglycinate, vitamin D, zinc, selenium, and vitamin C complete the core nutritional picture. Energy Formula covers all of these in their active, bioavailable forms - designed for exactly this pattern of accumulated nutritional depletion.

How do you know which type you have?

The honest answer is that most women have more than one. HPA axis fatigue and nutritional depletion almost always appear together. Blood sugar dysregulation compounds mitochondrial fatigue. Iron deficiency worsens thyroid function. The patterns overlap and reinforce each other.

A useful starting point is to notice when the fatigue hits and what it feels like:

• Wired in the evening, flat in the morning, broken sleep → HPA axis
• Pervasive heaviness that caffeine does not touch → mitochondrial
• Worse on exertion, headaches, hair changes → iron/ferritin
• Cold all the time, weight changes, constipation → thyroid
• Energy crashes after meals, sugar and caffeine cravings → blood sugar
• Gradual, slow decline over months or years → nutritional depletion

If fatigue is severe, persistent, or accompanied by symptoms that concern you, please see your GP before starting any supplement regime. Some causes of fatigue need medical investigation and management. Blood tests for thyroid, ferritin, B12, vitamin D, and fasting glucose are a reasonable starting point and always worth asking for.

What nutritional support can do

For fatigue that is driven by the patterns above, particularly for the combination of HPA axis dysregulation, nutritional depletion, and mitochondrial stress that is so common in women managing demanding lives, comprehensive nutritional support makes a real difference. Food comes first, but quality supplements have their place.

Energy Formula isn't a treatment, but when diet, sleep, and stress management form the foundation, and the right nutritional support sits alongside them, the cumulative effect on energy can be significant. For many women, it is the piece that finally shifts the dial.

Shop Energy Formula HERE or take the quiz to find the right formula for you HERE.

References

1. Langade D, Kanchi S, Salve J, Debnath K, Ambegaokar D. Efficacy and safety of ashwagandha (Withania somnifera) root extract in insomnia and anxiety: a double-blind, randomized, placebo-controlled study. Cureus. 2019;11(9):e5797.
2. Panossian A, Wikman G. Evidence-based efficacy of adaptogens in fatigue, and molecular mechanisms related to their stress-protective activity. Curr Clin Pharmacol. 2009;4(3):198–219.
3. Zozina VI, Covantev S, Goroshko OA, Krasnykh LM, Kukes VG. Coenzyme Q10 in cardiovascular and metabolic diseases: current state of the problem. Curr Cardiol Rev. 2018;14(3):164–174.
4. Hirsch KR, Smith-Ryan AE, Roelofs EJ, Trexler ET, Mock MG. Cordyceps militaris improves tolerance to high-intensity exercise after acute and chronic supplementation. J Diet Suppl. 2017;14(1):42–53.
5. Krayenbuehl PA, Battegay E, Breymann C, Furrer J, Schulthess G. Intravenous iron for the treatment of fatigue in nonanemic, premenopausal women with low serum ferritin concentration. Blood. 2011;118(12):3222–3227.
6. Szarfarc SC, de Cassana LMN, Fujimori E, Guerra-Shinohara EM, de Oliveira IMV. Relative effectiveness of iron bis-glycinate chelate (Ferrochel) and ferrous sulfate in the control of iron deficiency in pregnant women. Arch Latinoam Nutr. 2001;51(1 Suppl 1):42–47.

This article is for educational purposes only and does not constitute medical advice. Food supplements should not be used as a substitute for a varied, balanced diet or healthy lifestyle. If you are experiencing persistent fatigue, please speak to your GP before starting any new supplement. Some women have elevated iron or haemochromatosis and should not supplement with iron at all.