Persistent fatigue, a complaint often brought to general practitioners, affects approximately one in five individuals, according to medical experts. Differentiating this constant tiredness from normal exhaustion after exertion is key, as it signifies an underlying health issue.
Mental Health and Sleep Disorders
Depression is cited as the most frequent cause of ongoing fatigue. While typically associated with a chronic low mood, fatigue is a prominent symptom. A 2016 study indicated that depression was present in one-fifth of patients reporting constant tiredness. Other indicators of depression may include sleep difficulties, low self-esteem, and a diminished interest in activities that once brought pleasure. Antidepressant medications can also contribute to fatigue.
Sleep apnoea, characterized by intermittent relaxation of throat muscles that block the airway during sleep, disrupts sleep patterns and leads to exhaustion. Sufferers may experience snoring, and if they sleep alone, they might be unaware of the condition. Continuous positive airway pressure (CPAP) machines are a common medical treatment, and weight loss can also improve breathing and sleep quality.
Nutritional Deficiencies
Vitamin and mineral deficiencies are significant contributors to fatigue. Low iron levels are particularly common, especially among adult women, with a third affected compared to 3% of men, often due to heavy menstrual periods. Iron deficiency can lead to anaemia, presenting with pale or yellowish skin, shortness of breath, and fatigue. Hair loss can also be a symptom. Professors highlight that asking women experiencing fatigue about heavy periods can often point to iron deficiency, though blood tests are recommended for confirmation.
Vitamin B12 deficiency is another concern, primarily affecting individuals on vegan diets (about one-tenth of vegans) and those over 60, as the body's need for B12 increases with age. Symptoms include tiredness, headaches, indigestion, and concentration difficulties, with potential for nerve damage if left untreated. Folate deficiency, though less common, also impacts red blood cell production and DNA repair. Low vitamin D levels, often due to insufficient sunlight exposure, affect around one in six British adults, leading to fatigue. The NHS advises daily vitamin D supplements during autumn and winter months.
Diet, Hydration, and Hormonal Issues
A diet high in sugar, salt, and saturated fats, typical of Western eating habits, is strongly linked to fatigue. Ultra-processed foods can provide a short-term energy spike followed by a crash, and contribute to inflammation. Experts recommend increasing intake of fruits, vegetables, and seafood, which provide nutrients like magnesium, vitamin D, and fiber to improve energy levels.
Inadequate water intake is also a significant cause of fatigue. The NHS recommends six to eight glasses of water daily, but studies indicate a substantial portion of the population does not meet this target. Dehydration affects brain function and can lead to headaches alongside tiredness. Excessive consumption of caffeinated beverages can exacerbate dehydration.
Hormonal imbalances, particularly related to the thyroid, are another common cause of fatigue. Hypothyroidism, where the thyroid gland does not produce sufficient hormones, leads to fatigue. This condition affects millions and is more prevalent in older individuals and women with a family history. Diagnosis is typically made through a thyroid function blood test, and treatment with thyroxine hormone tablets is often effective.
Other Underlying Conditions
Sudden onset fatigue can be a symptom of diabetes, most commonly type 2, linked to lack of exercise and poor diet. Other signs include frequent urination and increased thirst. Diabetes can lead to serious long-term complications if blood sugar levels are not managed.
Inflammatory arthritis, an autoimmune condition where the immune system attacks healthy joint tissue, can also present with fatigue as an early symptom. Chronic kidney disease, often asymptomatic in its early stages, can cause fatigue and itchy skin as the kidneys begin to fail. Those with high blood pressure, diabetes, and obesity are at higher risk.
Chronic fatigue syndrome (CFS), a rare condition causing extreme fatigue lasting six months or more, is challenging to diagnose as it requires ruling out other causes. Triggers are believed to include stress, lack of sleep, or infection. Management focuses on preventing overexertion, which can worsen symptoms.
While rare, cancer can manifest with fatigue as a primary early symptom, as growing tumors consume body energy. However, fatigue is usually accompanied by other signs like lumps, unexplained weight loss, or changes in bodily habits. Medical professionals emphasize that while cancer is a possibility, it is an unlikely cause for most patients experiencing persistent tiredness.
Diagnostic Approaches
Experts recommend three key blood tests for individuals experiencing persistent fatigue: a full blood count to assess red blood cell health and oxygen-carrying capacity (which can indicate iron, B12, or folate deficiency), a thyroid function test, and an inflammatory marker test. These tests can help rule out a vast majority of potential causes.
In one case, Rachelle Smith, 40, experienced profound exhaustion, attributing it to early menopause. However, a private blood test revealed severe iron and vitamin D deficiencies. After starting supplements and increasing vitamin C-rich foods to aid iron absorption, her energy levels returned within two weeks.
Around half of those aged 25 to 34 report feeling exhausted – compared with only 23 per cent of those aged 55 or over.
