Why Am I Always Tired? Nutrient Deficiencies and Other Possible Causes

Ever wake up after eight hours of sleep and still feel like you could go straight back to bed? Or find yourself reaching for your third cup of coffee before lunchtime, wondering why your energy levels are nowhere close to where they should be?

If you've been asking yourself, why am I always tired and sleepy?, you're certainly not alone. But persistent fatigue is worth paying attention to, especially when it starts affecting your concentration, productivity, mood or everyday routine.

And here's something worth knowing: feeling tired all the time isn't necessarily a sign that you need more sleep. Sometimes, your body may be struggling with a nutrient deficiency. Other times, hormonal changes, poor sleep quality, blood sugar fluctuations or an underlying health condition could be contributing.

Let's look at what's actually happening inside your body and what might be behind those consistently low energy levels.

1. Iron deficiency: When your body struggles to carry oxygen 

Iron deficiency is one of the first nutritional factors worth investigating when you're constantly feeling tired, particularly if you experience heavy menstrual periods.

Iron is essential for producing haemoglobin, the protein in red blood cells that transports oxygen throughout your body. When iron levels become too low, oxygen delivery can become less efficient, leaving you feeling fatigued, weak or breathless.

Interestingly, you don't necessarily need to have anaemia to experience fatigue. A randomised controlled trial involving 198 menstruating women found that iron supplementation significantly reduced fatigue in women with low iron stores, even though they were not anaemic. [NIH]

Other signs to watch for: Dizziness, pale skin, headaches, shortness of breath and noticeable hair shedding.

2. Vitamin B12 deficiency: More than just low energy 

If you're always feeling weak and tired, vitamin B12 is another nutrient worth considering.

Vitamin B12 plays an important role in red blood cell formation, DNA synthesis and normal nervous system function. A deficiency can interfere with healthy red blood cell development, potentially leading to megaloblastic anaemia and reduced oxygen delivery.

It can also affect the nervous system, which explains why some people experience tingling or numbness alongside fatigue.

People following vegetarian or vegan diets, older adults and individuals with certain gastrointestinal absorption issues may be at greater risk. [NIH]

Other signs to watch for: Brain fog, numbness or tingling in the hands and feet, weakness and a sore tongue. 

3. Vitamin D deficiency: Could it be affecting your energy? 

Vitamin D is best known for its role in calcium absorption and bone health, but it also contributes to normal muscle function. 

Low vitamin D levels have been associated with fatigue, although this relationship does not mean every person experiencing tiredness has a deficiency.

There is some encouraging human research, too. A randomised, placebo-controlled trial involving 120 vitamin D-deficient adults found that vitamin D supplementation significantly improved self-reported fatigue over four weeks compared with placebo. [NIH]

Other signs to watch for: Muscle weakness, bone discomfort and generalised muscle aches.

4. Poor sleep quality: Eight hours doesn't always mean restorative sleep 

You might be spending enough time in bed but still waking up exhausted. Why?

Because sleep duration and sleep quality aren't the same thing.

Frequent awakenings, inconsistent sleep schedules, late-night screen exposure and conditions such as obstructive sleep apnoea can interfere with restorative sleep.

Sleep apnoea is particularly important to recognise. It causes repeated interruptions in breathing during sleep, which can lead to daytime sleepiness, morning headaches and difficulty concentrating. [NIH]

If you snore loudly, wake up gasping or feel excessively sleepy during the day, speak to a healthcare professional.

5. Thyroid imbalances: When your metabolism slows down 

Your thyroid gland produces hormones that regulate several metabolic processes, including how your body uses energy.

An underactive thyroid, medically known as hypothyroidism, can slow down these processes and contribute to persistent tiredness.

You may also notice unexplained weight gain, increased sensitivity to cold, constipation, dry skin and difficulty concentrating. [NIH]

The important part? Fatigue alone cannot confirm a thyroid problem. Blood tests measuring thyroid function can help establish whether your thyroid is involved.

6. Blood sugar fluctuations: Why am I always hungry and tired? 

Feeling hungry and tired at the same time can have several explanations.

Long gaps between meals, insufficient calorie intake and meals lacking adequate protein or fiber may leave you feeling hungry sooner than expected.

However, persistent hunger alongside fatigue, increased thirst and frequent urination can also be associated with diabetes, where the body cannot regulate blood glucose effectively.

Glucose is an important energy source for your cells, and insulin helps regulate its movement from the bloodstream into cells. [NIH]

If these symptoms occur together, don't dismiss them as ordinary hunger or an afternoon energy slump. Get your blood glucose levels checked.

7. Stress and mental exhaustion 

FAQs 

1. Why am I always tired even after sleeping for 8 hours? 

Poor sleep quality, sleep apnoea, iron deficiency, vitamin B12 deficiency, thyroid disorders and chronic stress can all contribute to tiredness despite adequate sleep duration.

2. Why am I always tired and sleepy during the day? 

Insufficient restorative sleep, irregular sleep schedules, certain medications and underlying health conditions can contribute to excessive daytime sleepiness.

3. Why am I always tired in the morning? 

Poor sleep quality, sleep apnoea, inconsistent sleep timings and certain medical conditions can make waking up feel particularly difficult.

4. Can vitamin deficiency make you feel tired all the time? 

Yes. Iron, vitamin B12 and vitamin D deficiencies can contribute to fatigue through different mechanisms, including impaired oxygen transport, abnormal red blood cell formation and altered muscle function.

5. Why am I always feeling weak and tired? 

Persistent weakness and fatigue may be associated with anaemia, nutrient deficiencies, thyroid disorders, infections, inadequate nutrition or poor sleep. Medical evaluation can help identify the cause.

6. Why am I always hungry and tired? 

Inadequate food intake, poorly balanced meals and long gaps between meals may contribute. However, persistent hunger with increased thirst and frequent urination warrants evaluation for diabetes.

7. Can low vitamin B12 cause dizziness and fatigue? 

Yes. Vitamin B12 deficiency can cause megaloblastic anaemia, which may contribute to fatigue, weakness and light-headedness. Dizziness can also have several other causes.

8. Which blood tests should I get if I am always tired? 

Depending on your symptoms, a healthcare professional may recommend a CBC, serum ferritin, vitamin B12, thyroid function tests, blood glucose or HbA1c and vitamin D testing.

9. Do multivitamin supplements help with constant tiredness? 

They may help address inadequate intake of certain nutrients, but they will not necessarily improve fatigue if you already have sufficient nutrient levels. The right approach depends on the underlying cause.

10. How can I improve my energy levels naturally?