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Why Am I Always Tired? 7 Everyday Causes (Food & Habits)

Why am I always tired? 7 food and habit causes to look at

Updated October 2026 · 7 minute read

Please note: I am not a doctor or a health professional. This article is for general information only and is not medical advice. It is based on the public health sources listed at the end. If you feel tired all the time, please talk to a qualified healthcare provider.

Waking up tired, dragging through the afternoon and still feeling drained at night is something most of us have experienced. Feeling tired from time to time is normal. But when it keeps going and you cannot explain why, it is worth looking at the everyday habits that may be behind it.

The Mayo Clinic notes that fatigue can most often be traced to one or more lifestyle issues, such as poor sleep habits or lack of exercise.[3] The NHS lists a similar set of causes, including not enough sleep, an unhealthy lifestyle, and stress.[4] Here are seven food and habit factors worth checking.

Key takeaways

  • Adults aged 18 to 60 are recommended to sleep at least 7 hours a night (CDC).
  • Iron and vitamin B12 deficiencies can cause tiredness, but the only way to know is a blood test.
  • B12 supplements do not appear to boost energy if you are not deficient (NIH).
  • Caffeine taken 6 hours before bed reduced sleep by more than an hour in one study.
  • If unexplained tiredness lasts and does not improve, see a doctor (NHS).

1. Not Getting Enough Sleep

adults need 7 or more hours of sleep, according to the CDC

This is the most obvious cause, and the easiest to underestimate. The CDC lists 7 or more hours per night as the recommendation for adults aged 18 to 60, based on a joint consensus statement from the American Academy of Sleep Medicine and the Sleep Research Society.[1] For adults over 60, the CDC's ranges are 7 to 9 hours (61 to 64 years) and 7 to 8 hours (65 and older).[1]

What to look at: a consistent bedtime, and turning off screens at least an hour before bed.[2]

2. Low Iron

iron helps blood carry oxygen

Iron is used to make hemoglobin, the protein in red blood cells that carries oxygen around your body.[6] According to the NIH Office of Dietary Supplements, people with iron deficiency anemia may experience weakness, fatigue and difficulty concentrating.[5] Harvard's Nutrition Source lists women who are pregnant or menstruating among the groups at higher risk.[7] The NIH also notes that how much iron you need depends on your age, your sex, and whether your diet is mostly plant-based.[6]

What to look at: iron deficiency is diagnosed with a blood test (the NIH describes serum ferritin as a key measure).[5] If you suspect low iron, ask a doctor to test it rather than starting supplements on your own.

3. Low Vitamin B12 or Vitamin D

vitamin B12 comes naturally only from animal foods

Vitamin B12. The NIH says a B12 deficiency may make you feel tired or weak.[8] Only animal foods contain B12 naturally, so people who eat little or no animal foods, such as vegetarians and vegans, are at higher risk. Older adults and people with certain digestive conditions or stomach surgery are also at risk, because absorption can be affected.[8][9] Symptoms can take several years to appear.[9] Important: the NIH states that B12 supplements appear to have no beneficial effect on performance when you are not deficient, so they are not an automatic energy fix.[9]

Vitamin D. In teens and adults, the NIH explains that vitamin D deficiency causes osteomalacia, a disorder that causes bone pain and muscle weakness.[10] The Cleveland Clinic lists fatigue among the possible signs in adults, but adds that many people have no symptoms at all.[11] The NIH also warns that very high vitamin D levels, almost always caused by too many supplements, can be harmful.[10]

What to look at: a varied diet, and a blood test with your doctor before taking high-dose supplements.

4. Not Drinking Enough Water

mild dehydration and concentration

The Mayo Clinic Health System notes that dehydration can cause fatigue, along with dry mouth and skin and nausea.[13] A study of 25 healthy young women in the Journal of Nutrition found that mild dehydration (about 1.4% of body weight, induced by exercise) was linked to worse mood, a higher perceived difficulty of tasks, lower concentration and headaches.[12] This study measured mood and concentration, not tiredness directly, and the dehydration was induced under controlled conditions.

What to look at: drink regularly through the day, especially when it is hot or when you are active.

5. Skipping Meals or Eating Poorly

balanced meals and steady energy

The Mayo Clinic lists eating poorly as one of the lifestyle factors linked to fatigue.[3] Australia's Better Health Channel adds that "quick fix" foods, such as chocolate bars or drinks high in caffeine or sugar, only give a short-term energy boost that quickly wears off and may contribute to fatigue.[14] A moderate, well-balanced diet may improve health and sleep.[15]

What to look at: regular, balanced meals instead of relying on sugary snacks to get through the day.

6. Caffeine and Alcohol

caffeine six hours before bed can cut sleep

Caffeine. It can feel like a quick fix, but timing matters. In a small clinical study, 400 mg of caffeine taken even six hours before bedtime reduced total sleep time by more than an hour, and participants were not aware of the loss.[16][17] The FDA cites 400 mg a day, about two to three 12-ounce cups of coffee, as an amount not generally associated with negative effects for most adults.[18] Sensitivity varies from person to person.

Alcohol. A scientific review of experiments in healthy volunteers found that alcohol shortens the time it takes to fall asleep but increases sleep disruption in the second half of the night.[19] Better Health Channel also notes that alcohol disturbs normal sleep patterns.[14]

What to look at: keep caffeine to the morning or early afternoon, and notice how you feel the day after drinking alcohol.

7. Not Moving Enough (or Too Much)

WHO physical activity recommendation for adults

The Mayo Clinic lists both too little and too much physical activity among the lifestyle causes of fatigue.[3] The World Health Organization recommends that adults do at least 150 to 300 minutes of moderate-intensity aerobic activity per week, or an equivalent amount of vigorous activity.[22]

Does exercise really boost energy? The evidence is encouraging but not uniform. A meta-analysis in Psychological Bulletin concluded that chronic exercise increased feelings of energy and lessened feelings of fatigue overall, although studies using a placebo control and exercise alone found no effect.[20] In a randomized trial of sedentary young adults who reported persistent fatigue, six weeks of low and moderate exercise training improved feelings of energy.[21]

What to look at: start small, such as a daily walk, and build up gradually.

When Tiredness Needs a Doctor

The NHS advises that if you cannot explain why you are tired, it has been going on for a while and it is not getting better, it may be a sign of a medical condition, and you should see a GP rather than self-diagnose.[4] Fatigue can also be caused by medicines or be linked to depression, and sometimes it is a symptom of an illness that needs treatment.[3] Consider seeing a healthcare provider if tiredness affects your daily life and simple changes do not help.[15]

Final Thoughts

Most people can improve their energy by working on the basics: enough sleep, balanced meals, enough water, regular movement, and a sensible approach to caffeine and alcohol. But if you have tried these and still feel exhausted, do not keep guessing. Get checked.

Frequently Asked Questions

How many hours of sleep do adults need?

The CDC lists 7 or more hours per night for adults aged 18 to 60, 7 to 9 hours for ages 61 to 64, and 7 to 8 hours for those 65 and older.[1]

Can dehydration make you feel tired?

Yes. The Mayo Clinic Health System lists fatigue among the effects of dehydration.[13] In a controlled study, mild dehydration also worsened mood and concentration in healthy young women.[12]

How much caffeine is too much?

The FDA cites 400 mg a day, about two to three 12-ounce cups of coffee, as an amount not generally associated with negative effects for most adults, though sensitivity varies.[18] Timing matters too: in one study, caffeine six hours before bed still reduced sleep.[16]

Can vitamin B12 supplements give you more energy?

Only if you are deficient. The NIH states that B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit.[9]

When should I see a doctor about tiredness?

The NHS advises seeing a GP if you cannot explain your tiredness, it has gone on for a while and it is not getting better.[4]

Sources

  1. CDC. About Sleep. cdc.gov/sleep/about. (Cites: Watson NF, et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the AASM and SRS. Sleep 2015;38(6):843-844.)
  2. ThedaCare. How Much Sleep Do I Need? thedacare.org
  3. Mayo Clinic. Fatigue: Causes. mayoclinic.org
  4. NHS (UK). Tiredness and fatigue. nhs.uk
  5. NIH Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals. ods.od.nih.gov
  6. NIH Office of Dietary Supplements. Iron: Fact Sheet for Consumers. ods.od.nih.gov (PDF)
  7. Harvard T.H. Chan School of Public Health. Iron, The Nutrition Source. nutritionsource.hsph.harvard.edu
  8. NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Consumers. ods.od.nih.gov
  9. NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals. ods.od.nih.gov
  10. NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Consumers. ods.od.nih.gov
  11. Cleveland Clinic. Vitamin D Deficiency. my.clevelandclinic.org
  12. Armstrong LE, et al. Mild dehydration affects mood in healthy young women. The Journal of Nutrition 2012;142(2):382-388. PubMed
  13. Mayo Clinic Health System. What's the latest buzz on energy drinks? mayoclinichealthsystem.org
  14. Better Health Channel (State Government of Victoria, Australia). Fatigue. betterhealth.vic.gov.au
  15. Medical News Today. Fatigue: Why am I so tired, and what can I do about it? medicalnewstoday.com
  16. Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine 2013;9(11):1195-1200. jcsm.aasm.org
  17. American Academy of Sleep Medicine. Late afternoon, early evening caffeine can disrupt sleep at night (press summary of Drake et al., 2013). sciencedaily.com
  18. U.S. Food and Drug Administration. Spilling the Beans: How Much Caffeine Is Too Much? fda.gov
  19. Ebrahim IO, Shapiro CM, Williams AJ, Fenwick PB. Alcohol and sleep I: effects on normal sleep. Alcoholism: Clinical and Experimental Research 2013;37:539-549. Wiley Online Library
  20. Puetz TW, O'Connor PJ, Dishman RK. Effects of chronic exercise on feelings of energy and fatigue: a quantitative synthesis. Psychological Bulletin 2006;132(6):866-876. ERIC record
  21. Puetz TW, Flowers SS, O'Connor PJ. A randomized controlled trial of the effect of aerobic exercise training on feelings of energy and fatigue in sedentary young adults with persistent fatigue. Psychotherapy and Psychosomatics 2008;77(3):167-174. Karger
  22. World Health Organization. WHO Guidelines on Physical Activity and Sedentary Behaviour (2020), executive summary. NCBI Bookshelf

This article is for educational purposes only and does not replace professional medical advice, diagnosis or treatment.

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