Fatigue is one of those symptoms we all live with at some point — a rough night, a busy week, a stressful life event. But when tiredness feels like a constant companion rather than a temporary setback, it’s easy to chalk it up to “normal” and keep pushing. I’ve learned, through both my work and conversations with readers, that persistent fatigue can hide deeper issues. Below I share eight often-overlooked medical signs that, when present alongside ongoing fatigue, should prompt a visit to your doctor.
Why persistent fatigue deserves attention
Before diving into the specific signs, a quick note about why this matters. Chronic tiredness doesn’t just make life less enjoyable — it can be an early indicator of underlying medical conditions that are treatable or manageable. I aim to help you spot the things that commonly get missed so you can bring more precise information to your clinician and speed up diagnosis and relief.
Unexplained weight changes
Weight that shifts without a clear cause — either loss or gain — paired with fatigue is more than a cosmetic concern. I’ve seen people assume stress or diet changes are behind it, but unexplained weight loss can point to conditions like hyperthyroidism, diabetes, cancer, or chronic infection. Unexplained weight gain, especially if accompanied by swelling or fluid retention, could suggest hypothyroidism, heart failure, or kidney disease.
If you notice a steady change of more than a few kilos over a few months alongside low energy, that’s a red flag worth discussing with your doctor. Bring records or photos if you can — objective data helps clinicians.
Persistent shortness of breath or breathlessness on light exertion
Feeling winded climbing a flight of stairs can be age-related or fitness-related, but if you’re short of breath doing activities that never used to faze you, and you’re also fatigued, consider medical causes. Anemia, heart disease, chronic lung disease (like COPD), pulmonary hypertension, and even sleep-disordered breathing can cause both breathlessness and fatigue.
Note details such as when the breathlessness occurs, whether it’s worse lying down, and if you’ve had recent chest pain or palpitations. These details guide the urgentness and type of tests your clinician will order.
Brain fog, memory slips, or slow thinking
Mental fatigue — difficulty concentrating, forgetfulness, and slowed thinking — often gets labeled as "stress" or "normal aging." While stress can certainly cause cognitive symptoms, when brain fog comes with persistent physical fatigue, think about underlying causes like thyroid disease, vitamin B12 deficiency, long COVID, depression, or autoimmune conditions such as lupus.
Keeping a simple symptom diary noting times when concentration drops and what you're doing helps your clinician differentiate between sleep deprivation, mood disorders, and neurological or metabolic causes.
Unusual bruising or bleeding
Finding unexplained bruises, frequent nosebleeds, or heavier-than-normal menstrual bleeding alongside fatigue can indicate a blood disorder. Low platelets, clotting factor deficiencies, or bone marrow problems (including leukemia) sometimes present with tiredness because the body’s blood supply or oxygen-carrying capacity is affected.
Take note of the pattern and any family history of bleeding disorders — this information is crucial for targeted blood tests like a full blood count (FBC), clotting profile, and blood smear.
New or changing pain that disrupts sleep
Pain and poor sleep have a mutually reinforcing relationship: chronic pain fragments sleep, and lack of restorative sleep fuels fatigue and pain sensitivity. If you have a new pattern of pain — for example, joint pain with morning stiffness, chest pain, or abdominal pain — it’s important not to normalize it. Conditions like rheumatoid arthritis, inflammatory bowel disease, musculoskeletal disorders, or cardiac issues can cause both pain and systemic fatigue.
Describe the timing, triggers, and what eases the pain when you talk to your doctor. Night pain that wakes you or pain with systemic symptoms (fever, weight loss) needs prompt attention.
Unrefreshing sleep and loud snoring
Many people with obstructive sleep apnoea (OSA) report loud snoring, gasping during sleep, and unrefreshing rest despite spending adequate time in bed. OSA causes fragmented sleep and daytime sleepiness and is linked to cardiovascular disease and metabolic dysfunction. I often recommend that readers with persistent fatigue who snore loudly or wake gasping talk to their GP about a sleep assessment.
Wearables like Fitbit and Apple Watch sometimes flag abnormal sleep patterns, but a proper sleep study (polysomnography) is the diagnostic standard. Treatment options, from CPAP to mandibular advancement devices, can dramatically improve energy levels.
Persistent gastrointestinal symptoms
Chronic diarrhea, constipation, bloating, or abdominal pain with fatigue can point to malabsorption issues (like celiac disease), chronic infections, inflammatory bowel disease, or even pancreatic insufficiency. If your energy is low and your stool or appetite has changed, bring stool records and a list of foods that worsen or improve symptoms.
Tests may include coeliac serology, stool calprotectin, endoscopy, or breath tests for small intestinal bacterial overgrowth (SIBO). Addressing gut health often relieves fatigue because your body can better absorb nutrients and manage inflammation.
Low mood, anxiety, or loss of interest in activities
Mood disorders are both a cause and consequence of fatigue. Depression often presents as tiredness, low motivation, and changes in appetite or sleep. Anxiety can disrupt sleep and produce chronic hyperarousal, leaving you exhausted. I tell readers that mental health symptoms aren’t “less medical” than a broken bone — they’re real, treatable, and worth medical attention.
If you’re experiencing persistent low mood, hopelessness, or an inability to enjoy activities, tell your doctor. Treatments like cognitive behavioural therapy (CBT), SSRIs, lifestyle changes, and structured activity plans can significantly improve energy levels.
Quick reference table: signs, possible causes, and common initial tests
| Sign | Possible causes | Initial tests often ordered |
|---|---|---|
| Unexplained weight change | Thyroid disease, diabetes, cancer, heart/kidney disease | TSH, HbA1c, CBC, basic metabolic panel |
| Shortness of breath | Anemia, heart disease, lung disease, sleep apnoea | Chest X-ray, ECG, CBC, BNP, spirometry |
| Brain fog | B12 deficiency, thyroid issues, long COVID, depression | B12, TSH, CRP, depression screening |
| Unusual bleeding | Platelet disorders, clotting issues, marrow disorders | FBC, coagulation screen, peripheral smear |
| Unrefreshing sleep/snoring | Obstructive sleep apnoea | Sleep study referral, oximetry |
If any of these signs ring true for you, prepare for your appointment by jotting down timeline details, symptom patterns, and any relevant family history. That level of detail often shortens the diagnostic journey. And while tests and referrals can feel overwhelming, early detection of the causes behind chronic fatigue opens the door to targeted treatments that can restore energy and quality of life.
