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what deficiency causes tiredness

Several nutrient deficiencies are well-known for causing ongoing tiredness and low energy, especially if sleep and stress don’t fully explain how you feel.

Quick Scoop

If you’re asking “what deficiency causes tiredness,” the usual suspects are:

  • Iron deficiency (including iron-deficiency anaemia)
  • Vitamin B12 (and other B vitamins like B6, folate/B9)
  • Vitamin D
  • Magnesium
  • Sometimes: iodine, potassium, omega‑3s and vitamin C also play a role in fatigue.

Think of your body like a phone battery: these nutrients are the “charging cable.” If they’re low, you never get back to 100%, no matter how long you “plug in” (sleep).

The Big Ones That Make You Tired

1. Iron deficiency

  • Iron helps red blood cells carry oxygen; when it’s low, your tissues are literally under‑supplied with oxygen, so you feel drained and out of breath easily.
  • Common signs: heavy fatigue, pale skin, dizziness, shortness of breath on exertion, headaches, hair loss, rapid heartbeat.
  • Typical sources: red meat, organ meats, beans, lentils, spinach, fortified cereals; vitamin C (citrus, peppers) improves absorption.

2. Vitamin B12 (and other B vitamins)

  • B12 is crucial for red blood cell production and nervous system function; low levels cause fatigue, weakness and sometimes numbness or tingling.
  • Folate (B9) and other B vitamins (B2, B3, B5, B6) are involved in energy metabolism; low intake can cause “tired but wired,” brain fog and low stamina.
  • Main sources: meat, fish, eggs, dairy for B12; leafy greens, beans, whole grains for other B vitamins.

3. Vitamin D

  • Vitamin D helps muscle function and supports many processes that influence energy, mood and immunity; deficiency is extremely common worldwide and strongly linked to fatigue.
  • Signs can be vague: low mood, muscle weakness, bone aches and general exhaustion.
  • Sources: sunlight exposure, fatty fish, fortified milk or plant milks, and supplements when prescribed.

4. Magnesium

  • Magnesium is involved in hundreds of reactions, including converting food into ATP (your body’s usable energy), muscle relaxation and nervous system regulation.
  • Low magnesium can cause physical and mental fatigue, muscle cramps, poor sleep and sometimes heart rhythm issues in more severe cases.
  • Foods: nuts, seeds, whole grains, legumes, dark leafy greens.

Other Deficiencies That Can Add To Fatigue

Even if the “big four” are okay, other shortfalls can still worsen tiredness.

  • Iodine – needed for thyroid hormones that control metabolism; low iodine can make you feel sluggish, cold and tired.
  • Potassium – important for nerve and muscle function; deficiency can cause weakness and fatigue.
  • Omega‑3 fatty acids – support brain function and help reduce inflammation; low intake may contribute to low mood and tiredness.
  • Vitamin C – supports iron absorption and general energy; deficiency can cause weakness and fatigue.
  • Some sources also mention CoQ10 decline with age, which can contribute to low stamina, although this is usually discussed more in the context of supplementation than classic “deficiency.”

Quick Fact Table (Major Deficiencies & Tiredness)

[3][1] [1] [3][1] [3][1] [3][1] [1] [5][1] [5][1] [1] [1]
Nutrient How it causes tiredness Common food sources
Iron Reduces oxygen delivery to tissues, leading to fatigue and breathlessness.Red meat, lentils, beans, spinach, fortified cereals.
Vitamin B12 / B9 Impaired red blood cell production and nerve function, causing weakness and brain fog.Meat, fish, eggs, dairy (B12); leafy greens, beans, fortified grains (B9).
Vitamin D Linked to muscle weakness, low mood and chronic fatigue.Sunlight, fatty fish, fortified milk/plant milks.
Magnesium Disrupts energy production and sleep, causing mental and physical exhaustion.Nuts, seeds, whole grains, green vegetables, legumes.
Iodine Lowers thyroid hormone levels, slowing metabolism and causing sluggishness.Iodised salt, seafood, seaweed, dairy.

Important: Tiredness Is Not Always A Deficiency

Nutrient issues are only one piece of the puzzle.

Other common causes include:

  1. Poor or fragmented sleep (sleep apnea, insomnia, irregular schedules).
  2. Chronic stress or burnout.
  3. Infections, thyroid disease, heart or lung conditions, diabetes or depression.
  4. Medications, high alcohol intake, or high-sugar diets that spike and crash blood sugar.

Because many of these overlap in symptoms, self‑diagnosing a single “deficiency” can be misleading.

What To Do If You’re Always Tired

If you feel persistently exhausted for more than a few weeks:

  1. See a healthcare professional
    • Ask about blood tests for iron, B12, folate, vitamin D, thyroid function and sometimes magnesium.
 * This is the safest way to find out if a deficiency is really there.
  1. Do not start high‑dose supplements blindly
    • Too much iron or some vitamins can be harmful, especially if you don’t actually need them.
 * A clinician can tailor doses and check interactions with any medicines you use.
  1. Support your diet and lifestyle
    • Eat a varied diet with vegetables, fruits, whole grains, healthy fats and protein to cover most nutrient bases.
 * Work on consistent sleep, stress management and gentle activity, which all interact with your energy levels.

If your tiredness is severe, suddenly worse, associated with chest pain, shortness of breath at rest, fainting, or thoughts of self‑harm, seek urgent medical help.

Bottom line: Several deficiencies can cause tiredness, but iron, B12, vitamin D and magnesium are the most common ones linked to feeling tired all the time. Only proper testing can confirm the cause for you, so treat supplements as support, not a substitute for medical evaluation.

Information gathered from public forums or data available on the internet and portrayed here.