What Nutrient Deficiency Causes Tiredness?

December 19, 2025 •

4 min read

According to a study published by the National Institutes of Health, deficiencies in several key vitamins and minerals are directly linked to persistent fatigue. If you're constantly asking "What nutrient deficiency causes tiredness?", the answer likely involves essential nutrients like iron, vitamin B12, or vitamin D that are crucial for energy production.

Quick Summary

Constant tiredness can be a symptom of a nutritional shortfall. This article explores the specific nutrient deficiencies, such as low iron, vitamin B12, and vitamin D, that can cause persistent fatigue and offers guidance on how to address them through diet and supplementation to restore energy.

Key Points

Iron is Crucial for Oxygen Transport: Iron deficiency, a common cause of anemia, impairs oxygen delivery to tissues, leading to extreme fatigue, weakness, and pale skin.
Vitamin B12 Supports Blood and Nerves: A lack of vitamin B12 can cause megaloblastic anemia and nerve damage, resulting in chronic tiredness, pins and needles, and difficulty concentrating.
Vitamin D Influences Energy and Mood: Low levels of vitamin D are associated with chronic fatigue, muscle weakness, and low mood, especially in those with limited sun exposure.
Magnesium is Key for Energy Metabolism: A deficiency in magnesium can disrupt energy production at the cellular level, causing tiredness, weakness, and muscle cramps.
Folate is Needed for Red Blood Cells: Similar to B12, folate is essential for healthy red blood cells, and its deficiency can lead to anemia and fatigue.
Consult a Doctor for Diagnosis: While diet can be a factor, only a healthcare professional can confirm a deficiency through testing and rule out other causes of fatigue.

Common Nutrient Deficiencies Linked to Tiredness

Persistent and unexplained tiredness can often be a warning sign that your body is lacking a critical nutrient. Fatigue is a common symptom associated with deficiencies because many vitamins and minerals play a central role in energy metabolism and oxygen transport throughout the body. When these systems are compromised, it can leave you feeling drained and sluggish, regardless of how much sleep you get.

Iron Deficiency Anemia

Iron deficiency is one of the most widespread nutritional deficiencies globally and a primary cause of fatigue. Iron is essential for producing hemoglobin, a protein in red blood cells that carries oxygen from your lungs to your body's tissues and muscles. When iron levels are low, oxygen delivery to your cells is impaired, leading to a condition called anemia. Symptoms of iron deficiency anemia include:

Extreme tiredness and weakness
Pale skin
Shortness of breath
Dizziness or lightheadedness
Restless legs syndrome

Best sources of iron:

Heme iron (highly absorbable): Red meat, poultry, and fish
Non-heme iron (less absorbable): Spinach, lentils, beans, fortified cereals, and tofu

Vitamin B12 Deficiency

Vitamin B12 is vital for red blood cell formation and neurological function. A deficiency can lead to a type of anemia called megaloblastic anemia, where red blood cells are abnormally large and unable to function properly, impairing oxygen transport and causing fatigue. This deficiency is particularly common in older adults, vegans, and people with gastrointestinal issues affecting absorption. Signs of a B12 shortfall include:

Extreme fatigue and weakness
Tingling or numbness in the hands and feet
Difficulty concentrating or memory problems
Mood changes, including depression

Best sources of B12:

Animal products: Fish, chicken, milk, eggs, and yogurt
Fortified options: Plant-based milks and cereals

Vitamin D Deficiency

Often called the "sunshine vitamin," vitamin D plays a crucial role in bone health, immune function, and mood regulation. Research has linked low vitamin D levels to chronic fatigue, muscle weakness, and depression. People with limited sun exposure, darker skin, or certain digestive issues are at higher risk. Signs of vitamin D deficiency may include:

Chronic tiredness and low energy
Muscle weakness and aches
Bone pain
Frequent illnesses

Best sources of Vitamin D:

Sunlight: Safe, moderate exposure
Dietary: Fatty fish (salmon, tuna), egg yolks, and fortified foods

Magnesium Deficiency

Magnesium is involved in over 300 biochemical reactions in the body, many of which are related to energy production. A deficiency can disrupt cellular energy generation, leading to tiredness and muscle weakness. Symptoms of a magnesium shortfall can include:

Fatigue and weakness
Muscle cramps and twitching
Migraines
Anxiety and irritability

Best sources of magnesium:

Dark leafy greens, nuts, seeds, whole grains, and dark chocolate

Folate (Vitamin B9) Deficiency

Like vitamin B12, folate is essential for red blood cell formation and DNA synthesis. A lack of folate can lead to megaloblastic anemia, causing fatigue and irritability. Folate deficiency is a particular concern during pregnancy due to increased demand.

Best sources of folate:

Leafy green vegetables (spinach, kale), legumes (lentils, beans), and fortified grains

Table: Nutritional Deficiencies and Their Impact on Fatigue


Nutrient	Primary Function	Symptoms of Deficiency	Dietary Sources
Iron	Oxygen transport via hemoglobin	Extreme tiredness, weakness, pale skin, shortness of breath	Red meat, lentils, spinach, fortified cereals
Vitamin B12	Red blood cell formation, nerve health	Chronic fatigue, tingling in extremities, cognitive issues	Meat, fish, dairy, eggs, fortified foods
Vitamin D	Calcium absorption, energy production	Low energy, muscle weakness, bone pain, mood changes	Sunlight, fatty fish, fortified milk
Magnesium	Energy metabolism, muscle function	Fatigue, muscle cramps, weakness, migraines	Leafy greens, nuts, seeds, whole grains
Folate (B9)	Red blood cell production, DNA synthesis	Fatigue, weakness, irritability	Leafy greens, legumes, fortified grains

What to Do About Nutrient-Related Tiredness

If you suspect that a nutritional deficiency might be the root cause of your fatigue, consider the following steps. It is important to note that self-diagnosis can be misleading, as other conditions can mimic these symptoms.

Consult a Healthcare Professional: The most important step is to talk to your doctor. They can order specific blood tests to accurately measure your vitamin and mineral levels, such as a complete blood count for anemia or serum levels for vitamin B12 and D.
Focus on a Balanced Diet: Incorporate a wide variety of nutrient-rich foods into your daily meals. For example, pair iron-rich foods with vitamin C sources to enhance absorption.
Consider Supplements (with caution): Supplements can be a fast and effective way to correct a diagnosed deficiency, but they should only be taken under medical supervision. Over-supplementation can be harmful, particularly with iron. Your doctor can recommend the correct dosage.
Improve Lifestyle Factors: While diet is crucial, other factors also impact energy. Ensure you prioritize good sleep hygiene, stay adequately hydrated, and get regular physical activity.

Conclusion: Your Path to More Energy

Understanding what nutrient deficiency causes tiredness can be the first step toward regaining your vitality. Conditions like iron-deficiency anemia and low levels of vitamin B12, vitamin D, and magnesium are frequently culprits behind persistent fatigue. By consulting a healthcare provider, undergoing proper testing, and making targeted changes to your diet, you can address these deficiencies and improve your energy levels. Remember that fatigue can have multiple causes, so a holistic approach, including lifestyle adjustments, is often most effective. Don't let chronic tiredness dictate your life; take proactive steps to nourish your body and feel your best.

For more detailed information on specific health conditions, the National Institutes of Health (NIH) is a reliable source.

Frequently Asked Questions

Iron deficiency is one of the most common nutrient deficiencies globally that causes tiredness. It leads to anemia by impairing the body's ability to produce hemoglobin, which is vital for carrying oxygen.

A vitamin B12 deficiency can cause fatigue by leading to megaloblastic anemia, where red blood cells are fewer and less effective at carrying oxygen. This directly impacts your energy levels and can also cause nerve problems.

Yes, low vitamin D levels are linked to chronic fatigue and low energy. Vitamin D is involved in energy production and muscle function, and a deficiency can lead to muscle weakness and persistent tiredness.

Magnesium is a key mineral involved in over 300 enzymatic reactions, many of which are crucial for producing and using cellular energy (ATP). Without sufficient magnesium, your body can't generate energy efficiently, causing fatigue and weakness.

Individuals following vegetarian or vegan diets are at higher risk for vitamin B12 deficiency, while those with heavy menstrual periods or certain digestive issues are more prone to iron deficiency. Older adults and those with limited sun exposure are also at risk for vitamin D deficiency.

If you suspect a nutrient deficiency, the best course of action is to consult a healthcare professional. They can perform blood tests to confirm the deficiency and recommend appropriate, safe steps for treatment, which may include dietary changes or supplements.

Eating a balanced, varied diet rich in whole foods is key. For example, pairing iron-rich foods with vitamin C sources improves absorption, and incorporating a range of B vitamin sources ensures better energy metabolism.