We’ve all had those mornings where the snooze button feels like our best friend.
But if that “heavy” feeling persists regardless of how much sleep you get, it’s rarely just about a late night. Constant fatigue, often called TATT (Tired All The Time), is one of the most common reasons people visit a GP.
Here are 10 medical and psychological reasons you might be feeling drained, and how to know when it’s time for professional help.
This is a leading cause of fatigue, especially in women of childbearing age or those with restricted diets.
What it is: A lack of iron leads to fewer red blood cells, which means your body struggles to transport oxygen to your tissues.
Treatment: Depends on the cause.
When to see a doctor: All patients with iron deficiency anaemia need to be fully assessed by a doctor. Why?
Note on causes.Iron deficiency anaemia has a cause, usually chronic bleeding. You need to find the cause, not just start iron tablets.
B12 is essential for nerve function and the production of DNA and red blood cells.
What it is: A deficiency often caused by diet (common in vegans) or malabsorption issues like pernicious anaemia.
Treatment: High-dose oral supplements or B12 injections (hydroxocobalamin) administered by a doctor.
When to see a doctor: If your fatigue is accompanied by a “pins and needles” sensation, a sore tongue, or memory fog.
Note on causes. This also has a cause. You need to find the cause, not just start injections or tablets.
Often called the “sunshine vitamin,” many people in northern latitudes are chronically low, especially in winter.
What it is: Vitamin D is crucial for bone health and immune function; low levels are strongly linked to muscle weakness and low mood.
Treatment: Safe sun exposure and daily vitamin D3 supplementation (usually 400–1000 IU).
When to see a doctor: If you experience dull, aching bone pain or frequent infections alongside your exhaustion.
Your thyroid gland acts as the “thermostat” for your metabolism. When it’s slow, everything else slows down too.
What it is: The thyroid gland doesn’t produce enough thyroxine (T4), dragging your energy levels down.
Treatment: Daily hormone replacement tablets (Levothyroxine) to restore normal levels.
When to see a doctor: If you’re gaining weight despite no diet changes, feeling unusually cold, or have dry skin.
High blood sugar levels can ironically leave your cells starving for energy.
What it is: When the body can’t move glucose from the blood into the cells, you lose your primary “fuel,” leading to exhaustion.
Treatment: Lifestyle changes, metformin, or insulin therapy, depending on whether it is Type 1 or Type 2.
When to see a doctor: If you are excessively thirsty (polydipsia) or find yourself using the bathroom much more frequently at night.
This isn’t just a “food intolerance”—it’s a serious autoimmune condition triggered by gluten.
What it is: Ingesting gluten causes the immune system to attack the lining of the small intestine, leading to poor nutrient absorption.
Treatment: A strict, lifelong gluten-free diet to allow the gut to heal.
When to see a doctor: If your fatigue is paired with persistent bloating, diarrhea, or unexplained weight loss.
Your kidneys are the unsung heroes of energy regulation and fluid balance.
What it is: Chronic Kidney Disease (CKD) or imbalances in minerals like potassium, sodium, calcium and magnesium can disrupt nerve and muscle function.
Treatment: Managing blood pressure, dietary adjustments, and addressing the underlying cause of CKD and/or electrolyte disurbance (often secondary to medication).
When to see a doctor: If you feel generally weak, or are short of breath or have swollen ankles (oedema).
Mental health problems are physically exhausting. The constant “high alert” of anxiety or the “low energy” of depression takes a toll.
What it is: Psychological distress affects sleep cycles and neurotransmitters like serotonin and dopamine, which regulate energy.
Treatment: A combination of Talk Therapy (CBT), exercise, and potentially antidepressant medication.
When to see a doctor: If you’ve lost interest in things you used to enjoy or feel a persistent sense of dread or hopelessness.
You might be “sleeping” for 8 hours, but your brain isn’t getting the rest it needs.
What it is: Your breathing repeatedly stops and starts during sleep, causing your brain to wake you up (even if you don’t remember it).
Treatment: Weight loss, side-sleeping, or using a CPAP (Continuous Positive Airway Pressure) machine.
When to see a doctor: If your partner says you snore loudly or gasp in your sleep, or if you wake up with a headache.
Myalgic Encephalomyelitis (ME) is a complex, long-term illness that is often misunderstood.
What it is: Severe, disabling fatigue that doesn’t improve with rest and often worsens after physical or mental effort (Post-Exertional Malaise).
Treatment: Focuses on “pacing” (energy management), symptom relief, and specialist support.
When to see a doctor: If your exhaustion has lasted more than 4 months and significantly limits your daily activities.
While many causes of fatigue are lifestyle-based (stress, poor diet), you should see your GP if:
The fatigue lasts longer than two to three weeks.
You have unexplained weight loss or fever.
You feel short of breath or have chest pains.
Rest and sleep do not improve your energy levels.
Concerning Potential Causes
“Could this be related to a nutrient deficiency?” (Specifically mention Iron, B12, and Vitamin D).
“Should we check my thyroid function (TSH levels)?”
“Is it possible my blood sugar levels are abnormal?” (Ask about an HbA1c test for diabetes).
“Could my kidneys be under stress?” (Ask about an eGFR or U&Es and bone biochemistry).
Concerning Treatment & Next Steps
“Which specific blood tests are you ordering, and what exactly do they screen for?”
“If my blood results come back ‘normal,’ what is the next step for investigating this fatigue?”
“Are any of my current medications or supplements known to cause drowsiness as a side effect?”
“Based on my symptoms, do I need a referral to a specialist (like an endocrinologist or sleep clinic)?”
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