Everyone feels worn out occasionally, but if you’re feeling tired all the time, struggling to focus, or waking up with no energy despite resting, it could be a sign that something deeper is going on. Many people dismiss ongoing fatigue as stress or lifestyle-related, but persistent exhaustion, especially when it’s paired with symptoms like tired all time nausea, dizziness, or when your eyes feel heavy and tired all the time, may point to an underlying medical condition.
At Medilabs, we regularly see patients who say they are always tired all the time, with no clear reason why. That’s why we’ve created a dedicated Tired All The Time blood test package, a comprehensive screening designed to uncover possible causes such as anaemia, thyroid disorders, vitamin deficiencies, or blood sugar imbalances.
In this guide, we’ll explore 10 common medical reasons behind constant fatigue and explain how our exclusive package of blood tests for tired all the time can help you find answers. Whether your results show tired all the time blood tests normal or reveal imbalances, having clarity is the first step towards regaining your energy.
Anaemia & Iron Deficiency
Anaemia is one of the most frequent medical explanations for feeling tired all the time, and it is particularly common in women, although it can affect anyone. Anaemia occurs when your body does not produce enough healthy red blood cells, or when your haemoglobin levels drop too low. Haemoglobin is the protein inside red blood cells that binds to oxygen and delivers it throughout your body. Without enough haemoglobin, your tissues are literally starved of oxygen, leaving you always tired all the time.
Why anaemia makes you feel exhausted?
If your oxygen supply is reduced, you may notice that even everyday activities such as climbing the stairs or walking short distances leave you breathless and weak. Many patients describe their eyes feel heavy and tired all the time, or that they experience tired all time nausea and dizziness. In more severe cases, you may feel your heart racing, experience pale skin, or suffer from headaches and poor concentration. All of these are signs that your blood is not carrying enough oxygen to meet your body’s needs.
Causes of iron deficiency
Iron deficiency is the leading cause of anaemia worldwide. Iron is essential for making haemoglobin, and when your iron stores run low, red blood cell production suffers. Common causes include:
- Dietary deficiency – not eating enough iron-rich foods (e.g. red meat, leafy greens, fortified cereals).
- Heavy menstrual periods – a very common cause in women of reproductive age.
- Pregnancy – increased iron demand to support the baby.
- Chronic blood loss – for example, from ulcers or internal bleeding.
- Poor absorption – certain gut conditions (e.g. coeliac disease, Crohn’s disease) can reduce iron uptake.
How blood tests can help
At Medilabs, our exclusive Tired All The Time blood test package checks for all the major markers that may explain your lack of energy feeling tired all the time:
- Haemoglobin – measures the oxygen-carrying capacity of your blood.
- Haematocrit – shows the proportion of red blood cells in your blood volume.
- Ferritin – reflects your iron storage levels. Low ferritin is often the earliest sign of deficiency.
- Iron, Transferrin, and TIBC (Total Iron Binding Capacity) – help assess how much iron is available and how well your body is transporting it.
- Red Blood Cell Count, MCV, MCH, MCHC – provide further detail on the size and quality of your red blood cells.
By analysing these results together, we can identify whether your fatigue is linked to iron deficiency anaemia or another blood-related condition. This is far more informative than routine checks, which may only look at haemoglobin.
Why testing matters?
Sometimes people assume they are anaemic and take iron supplements without confirmation. However, not all anaemia is due to iron deficiency. Taking iron unnecessarily can cause side effects and mask the real cause of your feeling tired all the time and dizzy. Our comprehensive testing ensures the right problem is identified, so you can get appropriate treatment and support.
Thyroid Disorders
Another common reason for feeling tired all the time is a thyroid imbalance. Your thyroid gland, located in the neck, produces hormones (T3 and T4) that control how fast or slow your body uses energy. When the thyroid is underactive (hypothyroidism) or overactive (hyperthyroidism), your energy levels can be dramatically affected.
Why thyroid problems cause fatigue
The thyroid is like your body’s energy regulator. If it slows down, so does everything else, from metabolism and digestion to heart rate and brain function. People with an underactive thyroid often describe being always tired all the time, even after a full night’s sleep. Their eyes feel heavy and tired all the time, they may feel cold, sluggish, and experience brain fog. On the other hand, an overactive thyroid can cause restlessness, palpitations, weight loss, and, paradoxically, exhaustion from an overworked system.
Symptoms to watch for
- Persistent tiredness and low energy
- Sensitivity to cold (hypothyroidism) or heat (hyperthyroidism)
- Weight gain or weight loss without explanation
- Dry skin, thinning hair, brittle nails
- Feeling anxious, irritable, or experiencing brain fog
- Feeling light headed and tired all time, particularly with rapid heartbeat or dizziness
These symptoms are often mistaken for stress or ageing, which is why blood testing is vital.
What blood tests can show
Our Tired All The Time blood test package includes a full thyroid panel to investigate whether your lack of energy feeling tired all the time is linked to thyroid issues:
- Thyroid Stimulating Hormone (TSH) – signals the thyroid to produce hormones; high levels usually mean an underactive thyroid.
- Free T4 (Thyroxine) – the main hormone produced by the thyroid; low levels suggest hypothyroidism.
- Free T3 (Tri-iodothyronine) – the active thyroid hormone that drives metabolism.
- Anti-Thyroid Peroxidase (Anti-TPO) Antibodies – checks for autoimmune thyroiditis (Hashimoto’s disease).
- Anti-Thyroglobulin Antibodies – another marker for autoimmune thyroid conditions.
Together, these markers give a complete picture of thyroid function and can explain why you’re feeling tired all the time and dizzy, gaining weight unexpectedly, or struggling with mood and focus.
Why testing matters?
Thyroid disorders often develop slowly and may go unnoticed for years. A standard check might only look at TSH, but this doesn’t always catch subtle or autoimmune thyroid problems. That’s why our panel includes antibodies and free hormone levels for a much clearer diagnosis. By identifying thyroid issues early, we can help you and your doctor manage them effectively, restoring energy and quality of life.
Vitamin B12 Deficiency
Low levels of Vitamin B12 are a well-known cause of persistent fatigue and weakness. This essential vitamin plays a key role in producing red blood cells, supporting the nervous system, and maintaining energy metabolism. Without enough B12, your body struggles to carry oxygen efficiently and your nerves can’t function properly, leaving you feeling tired all the time.
Why Vitamin B12 deficiency causes fatigue?
When B12 is low, red blood cells become large and fragile, reducing their ability to transport oxygen. This results in a type of anaemia called megaloblastic anaemia. Patients often describe being always tired all the time, even after resting. Some also experience neurological symptoms, such as tingling in the hands and feet, poor memory, or a sensation that their eyes feel heavy and tired all the time.
Because B12 also affects the brain and nerves, deficiency may lead to mood changes, irritability, and difficulty concentrating, which explains why many people complain of brain fog or feeling light headed and tired all time.
Symptoms to watch for
- Ongoing fatigue and weakness
- Pale or yellow-tinged skin
- Numbness or tingling in hands and feet
- Difficulty concentrating or memory problems
- Headaches and dizziness
- Tired all time nausea and loss of appetite in some cases
Causes of B12 deficiency
- Dietary deficiency – more common in vegetarians and vegans, as B12 is mainly found in animal products.
- Poor absorption – conditions like pernicious anaemia, coeliac disease, or Crohn’s disease can reduce absorption.
- Ageing – older adults may produce less stomach acid needed to absorb B12.
- Medications – certain drugs, such as metformin or proton pump inhibitors, can affect B12 absorption.
What blood tests can show
Our Tired All The Time blood test package includes a direct check of your Vitamin B12 levels, alongside folic acid and iron markers, to give a full picture of your nutritional status. This ensures that if your lack of energy feeling tired all the time is due to B12 deficiency, it will be clearly identified.
Why testing matters?
Vitamin B12 deficiency can mimic many other conditions. Some patients are told their tired all the time blood tests normal, when in fact, a detailed nutrient check was never performed. Untreated, B12 deficiency can lead not only to persistent fatigue but also irreversible nerve damage. By testing early, you can take corrective steps, whether through dietary changes, oral supplements, or injections recommended by your doctor.
Vitamin D Deficiency
Another often overlooked cause of feeling tired all the time is low Vitamin D. Known as the “sunshine vitamin,” Vitamin D plays a crucial role in bone strength, muscle health, immune function, and energy regulation. In the UK, where sunlight exposure is limited for much of the year, Vitamin D deficiency is extremely common.
Why Vitamin D deficiency causes fatigue
Vitamin D helps regulate calcium and phosphate balance, both vital for muscle function and energy production. When levels are low, people often feel physically weak, mentally drained, and always tired all the time. Muscle aches, frequent infections, and low mood are also common signs. Some patients even report that their eyes feel heavy and tired all the time, or that they struggle with persistent brain fog.
Symptoms to watch for
- Persistent fatigue and lack of motivation
- Muscle weakness and bone aches
- Low mood or seasonal depression
- Frequent colds or infections
- Difficulty concentrating or feeling light headed and tired all time
Causes of deficiency
- Limited sun exposure – the main source of Vitamin D is sunlight on the skin, and UK winters provide little opportunity for this.
- Dietary deficiency – Vitamin D is naturally present in few foods, mostly oily fish, fortified dairy, and egg yolks.
- Age – as we get older, the skin produces less Vitamin D.
- Medical conditions – gut disorders like coeliac or Crohn’s can reduce absorption.
What blood tests can show
Our Tired All The Time blood test package includes a direct measure of Vitamin D (25-OH). In the UK, the typical ranges are:
- >50 nmol/L – optimal
- 25–50 nmol/L – insufficient
- <25 nmol/L – deficient
Testing helps determine whether your lack of energy feeling tired all the time is linked to Vitamin D deficiency, or whether another cause is contributing.
Why testing matters?
Because the symptoms are vague, Vitamin D deficiency is often missed. Many people are told their tired all the time blood tests normal, without their Vitamin D ever being checked. Identifying a deficiency can make a dramatic difference, supplementation under guidance can restore energy, improve mood, and strengthen immunity.
Diabetes & Blood Sugar Imbalance
Blood sugar levels play a vital role in your energy and wellbeing. If they are too high, too low, or fluctuating, you may find yourself feeling tired all the time. Diabetes and prediabetes are common but often underdiagnosed conditions that can leave you always tired all the time, even after rest.
Why blood sugar imbalance causes fatigue?
Glucose is the body’s main source of energy. When your cells cannot use it properly, either because your body doesn’t make enough insulin or doesn’t respond to it effectively, energy production drops. This leaves you drained, with symptoms like feeling tired all the time and dizzy, blurred vision, and difficulty concentrating. Some people also experience tired all time nausea, shakiness, or sweating if their blood sugar dips too low.
Symptoms to watch for
- Constant tiredness and low energy
- Excessive thirst and frequent urination
- Feeling light headed, dizzy, or shaky
- Unexplained weight loss or gain
- Increased hunger but no energy boost
- Eyes that feel heavy and tired all the time
- Slow healing of cuts or infections
Causes and risk factors
- Type 1 diabetes – autoimmune condition where the body does not produce insulin.
- Type 2 diabetes – where the body becomes resistant to insulin or doesn’t produce enough.
- Prediabetes – early stage where blood sugar is higher than normal but not yet in the diabetic range.
- Lifestyle factors – poor diet, lack of exercise, and excess weight can all contribute.
What blood tests can show
Our Tired All The Time blood test package includes multiple markers to give a complete picture of your blood sugar health:
- Glucose – measures your current blood sugar.
- HbA1c – reflects your average blood sugar levels over the past 2–3 months.
- Insulin – shows how much insulin your body is producing.
- C-Peptide – helps determine whether your body is making insulin effectively.
Together, these tests identify whether your lack of energy feeling tired all the time is linked to poor glucose control, prediabetes, or diabetes.
Why testing matters?
Diabetes often develops silently, with tiredness being one of the earliest symptoms. Many patients are told their tired all the time blood tests normal, without their glucose or HbA1c being checked in detail. Identifying blood sugar imbalance early allows for lifestyle changes or treatment that can prevent serious complications, and restore energy levels.
Chronic Inflammation
Chronic inflammation is another hidden cause of feeling tired all the time. Unlike the short-term inflammation your body uses to fight infections or heal injuries, chronic inflammation lingers quietly in the background. It can drain your energy, weaken your immune system, and leave you always tired all the time, even when you think you’re otherwise healthy.
Why inflammation causes fatigue?
When your immune system is constantly active, it releases chemicals called cytokines. These chemicals interfere with normal energy production and can affect brain function, making you feel sluggish, foggy, and unwell. Many people describe eyes feel heavy and tired all the time, or a persistent sense of exhaustion that doesn’t go away with rest. Chronic inflammation has also been linked to dizziness, brain fog, and tired all time nausea.
Symptoms to watch for
- Ongoing tiredness and lack of motivation
- Unexplained aches and pains
- Brain fog or difficulty concentrating
- Low-grade fevers or night sweats
- Feeling light headed and tired all time without clear reason
Causes of chronic inflammation
- Autoimmune conditions – such as rheumatoid arthritis or Hashimoto’s thyroiditis
- Chronic infections – low-level infections that the body struggles to clear
- Obesity and poor diet – processed foods and excess sugar can trigger inflammatory responses
- Long-term stress – psychological stress can worsen inflammation
- Environmental factors – toxins, smoking, or pollution
What blood tests can show
Our Tired All The Time blood test package measures:
- C-Reactive Protein (CRP) – a key marker of inflammation in the body.
- White Blood Cell Count & Differential (neutrophils, lymphocytes, monocytes, eosinophils, basophils) – can reveal infection or immune overactivity.
By combining these results, we can determine whether hidden inflammation may be behind your lack of energy feeling tired all the time.
Why testing matters?
Because inflammation symptoms are vague, many people are told their tired all the time blood tests normal without ever having CRP checked. Identifying inflammation is crucial because it may point to an underlying condition that requires further treatment. It also provides a starting point for managing lifestyle factors like diet, exercise, and stress, which can help reduce inflammation and improve energy levels.
Kidney Issues
Your kidneys do more than just filter waste, they also help regulate fluid balance, electrolytes, and blood pressure. When the kidneys aren’t working properly, the imbalance can leave you feeling tired all the time. Even mild kidney problems can cause fatigue, nausea, and dizziness, making you feel always tired all the time, even after rest.
Why kidney issues cause fatigue?
Healthy kidneys remove waste products and toxins from the blood. If this function slows down, toxins can build up and affect your energy levels. The kidneys also help control levels of minerals such as sodium, potassium, and magnesium. When these electrolytes are out of balance, you may experience muscle weakness, confusion, or feeling light headed and tired all time. Some people also report tired all time nausea and fluid retention, which can worsen fatigue.
Symptoms to watch for
- Persistent tiredness and lack of energy
- Swollen ankles or puffiness around the eyes
- Nausea and loss of appetite
- Muscle weakness or cramps
- Changes in urination patterns (too much or too little)
- Dizziness and eyes feel heavy and tired all the time
Causes and risk factors
- High blood pressure – can damage kidney blood vessels over time
- Diabetes – a leading cause of kidney disease
- Chronic kidney disease (CKD) – often develops silently
- Dehydration – can impair kidney function temporarily
- Certain medications – may affect kidney performance
What blood tests can show
Our Tired All The Time blood test package includes key markers of kidney health and electrolyte balance:
- Creatinine – measures waste product filtered by the kidneys.
- eGFR (estimated Glomerular Filtration Rate) – shows how efficiently your kidneys are filtering blood.
- Urea – another waste product; high levels may signal kidney issues.
- Electrolytes – including sodium, potassium, chloride, phosphate, and magnesium. Imbalances can explain dizziness, weakness, and fatigue.
- Cystatin C – a sensitive marker for early kidney dysfunction.
Why testing matters?
Kidney issues often progress silently until significant damage has occurred. Routine checks may not catch subtle changes, leaving people told their tired all the time blood tests normal when the kidneys are already under strain. Our package provides a detailed picture of kidney health, ensuring that electrolyte imbalances and early dysfunction are not overlooked. Identifying problems early allows for timely treatment, lifestyle changes, and better energy management.
Ready for Next Steps?
Feeling worn out occasionally is normal, but being tired all the time is not something to ignore. As we’ve seen, constant fatigue can be caused by a wide range of medical issues, from anaemia and thyroid disorders to vitamin deficiencies, diabetes, kidney problems, or chronic inflammation. Each of these conditions can make you feel drained, dizzy, or like your eyes feel heavy and tired all the time, but the only way to know for sure is through proper investigation.
At Medilabs, we understand how frustrating it can be to be told your tired all the time blood tests normal when you still feel exhausted. That’s why we designed our exclusive Tired All The Time blood test package, a comprehensive screening that checks over 50 biomarkers linked to energy, metabolism, and overall health.
Whether you’re experiencing lack of energy feeling tired all the time, struggling with dizziness, or even tired all time nausea, this test can help uncover the real reason behind your symptoms. With fast results, a detailed explanation, and guidance on next steps, we give you the clarity you need to start feeling better.
Don’t let tiredness control your life. Book your Tired All The Time blood test at Medilabs today and take the first step towards restoring your energy and wellbeing.
