What might explain low energy?

Tiredness can have many causes. This page helps you explore questions about energy, but it cannot diagnose a cause or choose a treatment.

Feeling tired can mean being sleepy, finding it hard to concentrate or having less physical energy. Sleep, food, activity, medicines and health conditions can all play a part. Caffeine may make you feel more alert for a while. Low iron or vitamin B12 can matter for some people, but supplements are not a general treatment for tiredness.123

On this page
  1. Keep the question specific
  2. What a product claim cannot tell you
  3. When to seek individual care
  4. Alertness and caffeine
  5. Iron and tiredness
  6. Vitamin B12
  7. Sleep
  8. Sources
Follow this question
Energy & tiredness Choose a step to explore this subject in more detail.
  1. 1Keep the question specific
  2. 2What a product claim cannot tell you
  3. 3When to seek individual care
  4. 4Alertness and caffeine

Keep the question specific

What has changed for you? You might feel sleepy, struggle to concentrate, get short of breath during activity, feel weaker or feel generally unwell. These problems can have different causes.123

What a product claim cannot tell you

A label saying “energy support” does not prove a product treats ongoing tiredness. Check the ingredients and how much you take, and ask about possible interactions. Also check who was included in a study.

MOTS-c is sometimes called an energy peptide, but studies ask a more specific question: explore what is known. A change in a laboratory marker is not the same as feeling more energetic: see what SS-31 studies measured.123

When to seek individual care

Speak to a health professional about tiredness that is persistent, severe or unexplained. This matters especially if you also have breathlessness, bleeding, weight change, fever, nerve-related symptoms or major changes in mood.123

Seek emergency help immediately for severe difficulty breathing, such as gasping or being unable to get words out, or if the chest feels tight or heavy. Do not assume these symptoms are simply tiredness or low iron. New or worsening breathlessness also needs prompt medical advice.4

Alertness and caffeine

Caffeine can make you feel more alert, but it can also affect sleep. Count caffeine from coffee, tea, medicines and supplements. Read caffeine and alertness.

Iron and tiredness

Low iron can affect how the blood carries oxygen. Iron supplements can also be harmful when they are not needed. Read iron and tiredness.

Vitamin B12

Vitamin B12 helps keep blood and nerves healthy. For some people, the question is whether they get or absorb enough. Read vitamin B12.

Sleep

Poor or irregular sleep can affect energy and attention during the day. Explore sleep.

Sources, kept close.

Selected supporting sources; this is not a complete literature review.

  1. Health Benefits of Physical Activity for AdultsCenters for Disease Control and Prevention · public-health guidanceAccess checked 2026-11-05 · Source date: 2026-03-10 · General population guidance; it does not establish the effect of a particular supplement or provide individual medical advice.
  2. Healthy dietWorld Health Organization · public-health guidanceAccess checked 2026-11-05 · Source date: 2026-01-26 · Population guidance; it does not test individual supplements or establish a personal diet.
  3. Iron — ConsumerNIH Office of Dietary Supplements · consumer fact sheetAccess checked 2026-11-05 · The page was accessed on this date; no publication or update date was established from the page. A consumer overview; deficiency assessment and supplement decisions remain person- and product-specific.
  4. Shortness of breathNHS · UK patient guidanceAccessed 2026-11-06

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