Why Am I Always Tired? 7 Nutritional Reasons You're Exhausted (And What to Do About It)
You've had a full night's sleep. You've had your coffee. It's 10am — and you're already exhausted.
Sound familiar?
If you're a woman who's been feeling persistently tired, low in energy, or just not quite yourself, you're not alone. Fatigue is one of the most common complaints I hear from clients who come to see me at my Wimbledon clinic and online. And more often than not, the answer isn't simply "sleep more" or "stress less."
The truth is, chronic fatigue is almost always a sign that something deeper is going on — and nutrition plays a far bigger role than most people realise.
In this post, I'm going to walk you through seven of the most common nutritional reasons women feel exhausted, and what you can actually do about them.
1. Iron Deficiency (Even Without Anaemia)
Iron deficiency is the most common nutritional deficiency in women of reproductive age in the UK — and fatigue is its number one symptom. But here's the thing: you don't need to be clinically anaemic to feel the effects. Low-normal ferritin (your iron storage protein) can leave you feeling bone-tired, foggy-headed and breathless on the stairs — yet a standard GP blood test will often come back "normal."
What to look for: Persistent tiredness, pale skin, feeling cold, poor concentration, brittle nails, hair loss.
What to do: Ask your GP to test your ferritin specifically, not just haemoglobin. Good dietary sources include red meat, liver, lentils, spinach and fortified cereals. Pair plant-based iron sources with vitamin C to improve absorption — and avoid tea and coffee with meals, as they significantly inhibit iron uptake
2. Blood Sugar Imbalance
If your energy crashes mid-morning or mid-afternoon, if you feel irritable or shaky when you haven't eaten, or if you rely on sugar or caffeine to keep going — blood sugar dysregulation could be at the root of your fatigue.
When blood sugar spikes and crashes repeatedly throughout the day (often triggered by skipping meals, eating refined carbohydrates, or not getting enough protein), your energy yo-yos with it. Over time, this pattern is exhausting for your body.
What to look for: Energy slumps after meals, sugar cravings, irritability when hungry, reliance on caffeine, difficulty concentrating.
What to do: Prioritise protein and healthy fats at every meal to slow glucose release and keep blood sugar steady between meals. Reduce refined carbohydrates, eat breakfast within an hour of waking, and aim for structured meals rather than constant snacking — every time you eat, you trigger an insulin response, so grazing throughout the day can actually keep your blood sugar on a rollercoaster rather than stabilising it. Three satisfying, balanced meals is usually a far better strategy than eating little and often.
3. Magnesium Deficiency
Magnesium is involved in over 300 biochemical reactions in the body, including energy production, sleep regulation and stress response. And yet it's estimated that a large proportion of adults in the UK don't get enough from diet alone — especially those under stress, who drink alcohol regularly, or who have digestive issues.
Low magnesium can leave you feeling exhausted, wired-but-tired, muscle-achy and unable to sleep deeply — even when you're in bed for eight hours.
What to look for: Poor sleep quality, muscle cramps or twitches, anxiety, headaches, constipation, sensitivity to noise.
What to do: Increase dietary sources including dark leafy greens, pumpkin seeds, dark chocolate, avocado, almonds and black beans. Magnesium glycinate or bisglycinate supplements are generally well tolerated and absorbed — but it's worth speaking to a practitioner before supplementing.
4. B12 and B Vitamin Deficiency
The B vitamins — particularly B12, B6, folate and B1 — are essential for converting food into usable energy. Without adequate levels, you'll feel sluggish no matter how well you sleep or how healthy you eat.
B12 deficiency is particularly common in women who follow plant-based diets, those who take the contraceptive pill or metformin, and those over 50 (as absorption naturally declines with age). B12 deficiency can also mimic symptoms of depression and cognitive decline, which is why it's so important to test rather than guess.
What to look for: Extreme tiredness, brain fog, low mood, tingling in hands and feet, mouth ulcers, poor memory.
What to do: If you eat meat and dairy, B12 deficiency is less common but still possible. Ask your GP to test serum B12 and folate. Plant-based eaters should supplement with methylcobalamin B12 and look for fortified foods. A good quality B-complex supplement can also help support overall energy metabolism.
5. Thyroid Dysfunction (Often Missed in Women)
Your thyroid gland controls your metabolism — essentially how efficiently your body produces and uses energy. When it's underactive (hypothyroidism), everything slows down. And while a GP will often test TSH (thyroid stimulating hormone), this single marker can miss subclinical hypothyroidism, which leaves many women feeling exhausted, cold, and foggy despite being told their results are "normal."
What to look for: Fatigue that doesn't improve with rest, weight gain despite no change in diet, feeling cold all the time, dry skin and hair, hair loss, constipation, low mood.
What to do: Ask your GP for a full thyroid panel including TSH, free T3 and free T4. Nutritionally, iodine, selenium and zinc all support healthy thyroid function. Selenium in particular — found in Brazil nuts (just 2–3 per day covers your needs) — is crucial for converting inactive thyroid hormone into its active form.
6. Gut Health Issues Affecting Nutrient Absorption
You can eat the most nutritious diet in the world — but if your gut isn't absorbing nutrients effectively, you'll still be running on empty. Conditions like IBS, low stomach acid, SIBO (small intestinal bacterial overgrowth) and intestinal permeability can all impair your ability to absorb the very nutrients needed for energy production.
This is why so many women with digestive issues also struggle with fatigue — the two are far more connected than most people realise.
What to look for: Bloating, irregular bowel movements, food sensitivities, fatigue after eating, or a long history of digestive problems.
What to do: A nutritional therapist can help investigate gut health using functional testing such as comprehensive stool analysis or breath testing for SIBO. Dietary strategies to support the gut lining and microbiome — including reducing processed foods, increasing fibre diversity and supporting stomach acid — can make a significant difference to both digestion and energy levels.
7. Adrenal Fatigue and Chronic Stress
While "adrenal fatigue" isn't a formal medical diagnosis, HPA axis dysregulation — where the stress response system becomes dysregulated after prolonged periods of stress — is very real. Cortisol, your main stress hormone, follows a natural daily rhythm: it should be high in the morning to get you going and decline by evening. When this rhythm is disrupted, you may feel wired at night and exhausted in the morning, or simply flat and depleted throughout the day.
Nutritionally, chronic stress depletes key nutrients including vitamin C, magnesium and B vitamins — creating a vicious cycle of stress and fatigue.
What to look for: Feeling most tired in the morning, getting a "second wind" late at night, craving salty foods, difficulty coping with stress, low stamina.
What to do: Prioritise protein and healthy fats at breakfast to support cortisol rhythms. Adaptogenic herbs like ashwagandha and rhodiola (under practitioner guidance) can help regulate the stress response. Reducing caffeine, particularly in the afternoon, is also key.
So, What Should You Do Next?
If you're nodding along to several of these, the most important thing to know is this: you don't have to just put up with feeling tired.
Persistent fatigue is your body's way of telling you something needs attention — and with the right investigation and support, most women see a significant improvement in their energy levels within weeks.
As a registered nutritional therapist, I work with women in Wimbledon, South West London and online to get to the root cause of their fatigue — using in-depth health assessments, GP blood test interpretation and functional testing where needed.
If you're tired of being tired, I'd love to help.
👉 Book a free 20-minute discovery call and let's figure out what's really going on.
About the Author
Kirsty Larcombe is a registered nutritional therapist (Dip CNM, mANP, mGNC) based in Wimbledon, London. She specialises in helping women overcome fatigue, hormone imbalance and digestive issues through personalised, root-cause nutrition. Learn more about working with Kirsty →
Disclaimer: This blog post is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making changes to your diet or supplement regimen.
