Why am I always tired?
By Vita · fact-checked against NIH ODS
Vita is Vitaminico's AI nutrition coach. The nutrients below are mapped from the Vitaminico check, and every dose is checked against the NIH Office of Dietary Supplements; these pages have not yet been reviewed by our registered dietitians.
Constant tiredness has many causes; low iron, B12, vitamin D, or folate are common, checkable culprits — a simple blood test tells you for sure.
Likely nutrient gaps
These are the nutrients most often worth looking at first for this — not a diagnosis, just where the Vitaminico check starts. Read any one to see what it does, the best foods, and how much is too much.
Iron
8 mg/dayIron-deficiency anemia is the most common nutritional cause of fatigue worldwide — tiredness, weakness, and low energy are hallmark symptoms (NIH ODS). Risk is highest in menstruating women, during pregnancy, in people who don't eat meat/poultry/seafood, and with any blood loss or gut-absorption problem.
Vitamin B12
2.4 mcg/dayLow B12 causes fatigue and weakness through megaloblastic anemia (NIH ODS). Because the body stores years of B12, deficiency creeps in slowly. Risk rises with age, vegan/vegetarian diets, pernicious anemia, and long-term use of metformin or acid-reducing drugs.
Vitamin D
15 mcg/dayDeficiency causes muscle weakness (osteomalacia) and is associated with fatigue in research (NIH ODS). Common in people with little sun exposure, darker skin, covered skin, or who live at higher latitudes in winter.
Magnesium
420 mg/dayA mineral your body uses in 300+ enzyme reactions for muscle, nerve and energy function
What to eat
Food first is the safest place to start. Build your plate around a few of these everyday sources of the nutrients above:
- Iron: lean red meat, oysters, clams, or fortified breakfast cereal — pair plant sources (lentils, beans, spinach, tofu) with vitamin C (peppers, citrus) to absorb more
- B12: eggs, dairy, fish, and shellfish; if you eat plant-based, use fortified nutritional yeast, plant milks, or a B12 supplement (B12 is only reliably found in animal foods and fortified products)
- Folate: dark leafy greens, lentils and chickpeas, asparagus, and enriched/fortified grains
- Vitamin D: fatty fish like salmon, sardines, and mackerel, plus egg yolks and fortified milk or plant milk
- A practical anti-fatigue plate: spinach-and-lentil salad with grilled salmon and a squeeze of lemon — covers iron, folate, vitamin D, and vitamin C in one meal
- Fortified breakfast cereal or oatmeal with milk and an egg — an easy iron + B12 + vitamin D combo
How to confirm it (ask your clinician)
Being "always tired" is a symptom, not a diagnosis, so confirm the cause before treating it. See a clinician and ask for blood tests rather than guessing: a complete blood count (CBC) plus ferritin/serum iron for iron status, serum vitamin B12 (with methylmalonic acid if borderline), serum folate, and 25-hydroxyvitamin D. Fatigue also has non-nutritional causes — thyroid disease, sleep apnea, depression, diabetes, anemia from other sources, and medication side effects — so a doctor should rule those out too. Do not start high-dose iron or other supplements before testing: unneeded iron can be harmful and supplements can mask a B12 deficiency.
Not sure which gap is yours?
The free 2-minute Vitaminico check reads your symptoms across 9 body systems and names your most likely gap — food-first, no pills pushed.
FAQ
Is being always tired a sign of a vitamin deficiency?
It can be, but tiredness is a symptom with many possible causes — not a diagnosis. Iron, vitamin B12, folate, and vitamin D shortfalls are common, treatable contributors, but so are poor sleep, stress, thyroid problems, and other medical conditions. A blood test is the only way to know what's actually going on.
Which deficiency is the most common cause of fatigue?
Iron deficiency, and full iron-deficiency anemia, is the most common nutritional cause. Fatigue, weakness, and low energy are hallmark signs (per NIH Office of Dietary Supplements). It's especially common in people who menstruate, during pregnancy, and in those who don't eat meat, poultry, or seafood.
Can I just take supplements to fix my tiredness?
Not without testing first. Taking iron you don't need can cause harm, and supplementing folate can hide a B12 deficiency that keeps damaging nerves. Get the relevant blood tests, then take only what a clinician recommends at the dose they advise.
How long until I feel better after correcting a deficiency?
It varies. Iron stores can take weeks to a few months to rebuild; B12- or folate-related fatigue often improves within a few weeks of correction. If you've fixed a confirmed gap and still feel exhausted, go back to your doctor to look for other causes.
When should I see a doctor about constant tiredness?
See a clinician if fatigue lasts more than about two weeks, disrupts daily life, or comes with warning signs like shortness of breath, pale skin, a fast heartbeat, dizziness, or unexplained weight change — these can point to anemia or another condition that needs evaluation.
Vitaminico for iPhone
Get your full picture in the app
- A free 2-minute chat with Vita reads your symptoms — no food-logging, no needles
- Your top 3 likely nutrient gaps across the vitamins and minerals that matter
- A food-first plan: what to eat, where to get it, and what to skip
- No signup wall — the full check works the moment you open the app
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Educational, not medical advice. This page does not diagnose a deficiency or any condition. Symptoms can have many causes, nutritional and otherwise — only a clinician and, where needed, a blood test can confirm a real gap. Talk to your doctor before starting any high-dose supplement.