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Tiredness and low energy

Tiredness is the most searched symptom on this list and the least specific. It is a normal response to poor sleep, stress and overwork, a feature of dozens of medical conditions, and occasionally the presenting sign of a nutrient deficiency that a blood test would find in minutes.

General information only, not a diagnosis. A symptom is not proof of a deficiency — most symptoms here have many possible causes, and the common ones are rarely nutritional. Do not start a supplement to treat a symptom; the safe route is a blood test if one is warranted, and a doctor to interpret it. Use the red-flag list on each page, and see a clinician for anything that persists or worries you.

The reason tiredness attracts so much nutrition advice is that a handful of deficiencies genuinely do cause it, and those cases respond well to treatment. Iron deficiency is the clearest example: it produces fatigue before it produces anaemia, it is common in menstruating women, and correcting it makes a real difference to people who have it. Vitamin B12 and folate deficiencies do the same through a different route. All three are diagnosed with blood tests, not with symptom lists.

The trap is the inference in the other direction. "Iron deficiency causes tiredness" does not license "I am tired, so I am iron deficient". Most tired people are not deficient in anything. In population terms, by far the commonest causes of persistent tiredness are insufficient or fragmented sleep, an untreated sleep disorder such as obstructive sleep apnoea, depression and anxiety, thyroid disease, and the aftermath of an infection. Several of those are treatable and none of them improves with a supplement.

There is also a timing question worth asking before any of this. Tiredness that has come on over days after a virus behaves differently from tiredness that has been building for six months, and tiredness that is worst in the morning behaves differently from tiredness that arrives every afternoon at three. A doctor will ask about the pattern first, because the pattern narrows the list far faster than any single test.

What this page can usefully do is show you which nutrients are in the conversation, tell you honestly how strong each link is, and rank the foods richest in each of them from a public reference database. What it cannot do is tell you why you are tired.

Nutrients commonly discussed for tiredness

Each nutrient below is rated for how strong the evidence is that it relates to this symptom. "Relevant only if you are deficient" means it can matter when your level is genuinely low, but topping it up when it is not low does nothing.

Iron Relevant only if you are deficient

A genuine and common cause of fatigue when stores are low — and the reason ferritin is one of the first tests ordered for unexplained tiredness. Taking iron without a confirmed deficiency has no benefit and carries real risks for people who store iron too readily, so this is a blood test rather than a guess.

Full ranking: foods highest in iron.

Vitamin B12 Relevant only if you are deficient

Deficiency causes fatigue along with neurological symptoms, and becomes more likely with age, with a vegan diet, after certain gut surgery and with some long-term medicines. Again a blood test, not an inference.

Full ranking: foods highest in vitamin b12.

Folate Relevant only if you are deficient

Works alongside B12 in red blood cell production, and deficiency produces a similar picture. Worth knowing that treating a folate deficiency without checking B12 first can mask the B12 problem while the neurological damage continues — which is exactly why this belongs with a clinician.

Vitamin D Mixed evidence

Very commonly measured and very commonly low in northern winters. Whether correcting a moderately low level improves energy in someone without other symptoms is much less clear than the popularity of the test suggests; large trials in generally healthy adults have been underwhelming.

Full ranking: foods highest in vitamin d.

Magnesium Weak evidence

Widely marketed for energy and fatigue. Frank magnesium deficiency is uncommon in people eating a mixed diet, and the evidence that supplementing people who are not deficient improves energy is thin.

Full ranking: foods highest in magnesium.

Iodine Relevant only if you are deficient

Relevant only through the thyroid: iodine deficiency causes hypothyroidism, and hypothyroidism causes fatigue. There is no per-food iodine data in the reference database used on this site, so no ranking is shown. Dairy, white fish and iodised salt are the usual dietary carriers in Northern Europe. Too much iodine is also a thyroid problem, which is why this is not a nutrient to push.

Source: Foods richest in each nutrient: USDA FoodData Central SR Legacy (public domain), per 100 g · checked 2026-09-02

Causes that are usually more likely

Before a nutrient, these are the explanations a clinician would normally consider first for tiredness:

• Not enough sleep, or fragmented sleep
• An untreated sleep disorder — obstructive sleep apnoea is the classic missed one
• Depression, anxiety or chronic stress
• Thyroid disease
• Diabetes, coeliac disease, inflammatory conditions
• The weeks or months after a viral infection
• Medicines — including antihistamines, some blood pressure drugs and antidepressants
• Alcohol, including amounts people do not consider heavy

When to see a doctor

Treat these as reasons to seek a professional opinion rather than to self-treat:

• Tiredness with unexplained weight loss
• Breathlessness at rest, or on much less effort than usual
• Fever, night sweats, or a lump you can feel
• New or worsening shortness of breath, chest pain or palpitations
• Tiredness that has lasted weeks and does not improve with more sleep
• Feeling hopeless, or losing interest in things you used to enjoy

This list is not exhaustive, and a symptom that is severe, persistent or getting worse always deserves a professional opinion. If you feel very unwell, seek urgent care rather than reading further.

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