The most effective thing to take for fatigue depends on what’s causing it, but a few common deficiencies and habits account for the majority of everyday tiredness. Iron, vitamin B12, vitamin D, and magnesium are the nutrients most directly linked to energy production, and correcting even a mild shortfall in any of them can noticeably reduce fatigue. Beyond nutrients, adaptogens like ashwagandha and rhodiola have solid clinical evidence for stress-related and mental fatigue, and simple factors like hydration and caffeine timing play a larger role than most people expect.
Iron: The Most Common Nutritional Cause
Iron deficiency is the single most widespread nutrient deficiency worldwide, and fatigue is its hallmark symptom. Your body uses iron to build hemoglobin, the protein in red blood cells that carries oxygen to every tissue. When iron drops, your cells are essentially starved of oxygen, leaving you drained even after a full night’s sleep.
A blood test measuring ferritin (your stored iron) is the most reliable way to check. Levels below 15 micrograms per liter confirm iron deficiency. Levels between 15 and 30 indicate probable deficiency, and anything above 30 generally means iron stores are adequate. For older adults, the threshold is higher: ferritin below 50 warrants investigation. If you have a chronic inflammatory condition like rheumatoid arthritis or Crohn’s disease, ferritin needs to be above 70 to 100 to rule out deficiency, because inflammation artificially inflates the number.
If your levels are low, 15 to 30 mg of elemental iron per day is a reasonable starting dose for mild deficiency. Taking it every other day actually improves absorption compared to daily dosing, and it’s significantly easier on your stomach. Pair iron with vitamin C (a glass of orange juice works) and avoid taking it with coffee, tea, or calcium, all of which block absorption. If standard doses cause nausea or constipation, a low dose of 15 mg daily or 30 mg every other day has been shown to be effective even in older adults.
Vitamin B12: Especially If You’re Over 50 or Plant-Based
B12 is essential for producing red blood cells and maintaining the nerve pathways that regulate energy. Deficiency causes fatigue, brain fog, numbness or tingling in the hands and feet, and in severe cases, a type of anemia where red blood cells become abnormally large and inefficient. Blood levels below 200 to 250 pg/mL are considered subnormal, but marginal status (200 to 300 pg/mL) is surprisingly common, affecting up to 40% of people in Western countries, particularly those who eat little meat, fish, or dairy.
Your body’s ability to absorb B12 from food declines with age, which is why people over 50 are at higher risk regardless of diet. Vegans and vegetarians are at risk at any age since B12 is found almost exclusively in animal products. If you’re deficient, high-dose oral supplements of 1,000 mcg per day have been shown in clinical trials to normalize blood levels just as effectively as injections. For maintenance or mild deficiency, standard multivitamin doses (2.4 to 100 mcg) are often sufficient.
Vitamin D: The Overlooked Energy Factor
Low vitamin D is strongly associated with persistent fatigue, and most people who are deficient don’t realize it. In one clinical study of 28 patients diagnosed with chronic fatigue, 27 had insufficient or deficient vitamin D levels, averaging just 16 ng/mL. After vitamin D replacement therapy, their levels rose to an average of 28 ng/mL and 82% no longer met the diagnostic criteria for chronic fatigue. That’s a striking result for a single nutrient correction.
Most experts consider blood levels below 20 ng/mL deficient and 20 to 30 ng/mL insufficient. If you live in a northern climate, spend most of your time indoors, or have darker skin, you’re more likely to be low. A daily supplement of 1,000 to 2,000 IU of vitamin D3 is a common recommendation for adults with mild insufficiency, though your doctor may prescribe higher doses if your levels are very low. Taking it with a meal that contains fat improves absorption.
Magnesium: Fuel for Cellular Energy
Magnesium is involved in over 300 enzymatic reactions in your body, including the ones that convert food into usable energy at the cellular level. When levels drop, fatigue, muscle cramps, and poor sleep often follow. Surveys consistently show that a large portion of the population doesn’t meet the recommended daily intake through diet alone.
Not all magnesium supplements are equal. Chelated forms, where magnesium is bonded to amino acids (like magnesium glycinate or magnesium malate), are absorbed more efficiently than magnesium oxide, which is cheaper but passes through the gut without being well utilized. Magnesium glycinate tends to be gentler on the stomach and may support sleep. Magnesium malate is often recommended specifically for fatigue because malic acid plays a direct role in cellular energy production. A safe daily dose for most adults with healthy kidneys is 250 to 500 mg.
Ashwagandha for Stress-Driven Fatigue
If your fatigue is tied to chronic stress, poor sleep, or feeling constantly wired but exhausted, ashwagandha has the strongest clinical backing of any adaptogen. It works primarily by lowering cortisol, the stress hormone that, when chronically elevated, disrupts sleep quality and drains energy reserves.
Multiple randomized controlled trials have tested ashwagandha root extract at doses ranging from 225 to 600 mg per day. In several studies, participants taking 500 to 600 mg daily reported the greatest reductions in stress, fatigue, and sleeplessness compared to placebo. Benefits appeared to be dose-dependent, with higher doses outperforming lower ones. One trial in 120 overweight adults experiencing low energy found that ashwagandha significantly reduced fatigue over 12 weeks. In another, college students taking 700 mg daily for 30 days reported improved energy levels. Cortisol levels measurably dropped in multiple studies, including one where just 225 mg per day was enough to lower saliva cortisol compared to placebo.
Look for a root extract standardized to contain withanolides, the active compounds. Most studies used products providing between 1.5 and 15 mg of withanolides per dose. Allow at least four to eight weeks to notice a difference.
Rhodiola for Mental Fatigue
Rhodiola rosea is a different kind of adaptogen, best suited for mental exhaustion, brain fog, and the kind of fatigue that worsens under pressure. Where ashwagandha is calming, rhodiola is mildly stimulating.
In a two-week trial, 170 mg daily of rhodiola extract helped participants maintain higher levels of mental function on tasks like mental arithmetic compared to placebo. A separate study tested a single larger dose (370 to 555 mg) in military cadets undergoing sleep deprivation and found it significantly countered the effects of fatigue. A lower dose of 100 mg daily for 20 days showed more modest benefits in stressed students. The typical recommended dose is 200 mg twice daily, and staying under 600 mg per day is advised. Most supplements come in 100 to 500 mg tablets.
CoQ10 for Cellular Energy Production
Coenzyme Q10 is a compound your body makes naturally that plays a central role in mitochondrial energy production, the process by which your cells convert nutrients into the molecule that powers nearly everything you do. Your natural production of CoQ10 declines with age, and people taking statin medications for cholesterol often see significant drops.
Supplement doses typically range from 30 to 100 mg per day, which is considerably higher than what you’d get from food. CoQ10 is fat-soluble, so take it with a meal. While large-scale trials specifically targeting everyday fatigue are limited, it’s a well-tolerated option, particularly for adults over 40 or those on statins who notice unexplained tiredness.
Hydration: The Simplest Fix
Dehydration triggers fatigue faster than most people realize. Losing just 1.4% of your body weight in water (roughly one to two pounds for an average adult, easily lost through normal daily activity without drinking enough) measurably increases fatigue, worsens mood, and makes it harder to concentrate. At 2% loss, cognitive impairment becomes more pronounced, affecting memory, attention, and reaction time. You don’t need to be visibly thirsty or exercising hard to reach these levels. Sitting in an air-conditioned office, drinking coffee, and skipping water for a few hours can get you there.
If you’re chronically a little underhydrated, increasing your water intake may do more for your energy than any supplement. A reasonable target for most adults is around eight cups per day, adjusted upward for heat, exercise, and caffeine intake.
Caffeine: Timing Matters More Than Amount
Caffeine doesn’t give you energy. It blocks the receptors in your brain that detect a sleep-promoting chemical called adenosine. While it’s blocking those receptors, adenosine keeps building up. When the caffeine wears off, all that accumulated adenosine hits at once, which is why afternoon coffee can create a rebound crash that leaves you more tired than before.
The bigger issue is sleep disruption. Research shows that caffeine consumed less than eight to nine hours before bedtime reduces total sleep time, cuts into deep sleep, and shortens the restorative REM phase. Even a moderate intake of about 350 mg per day (roughly three cups of coffee) taken six hours before bed significantly impaired sleep quality in one study. If you go to bed at 10 p.m., your last cup should be no later than 1 to 2 p.m. to avoid quietly eroding the sleep that’s supposed to recharge you.
When Fatigue Signals Something Bigger
Everyday fatigue from poor sleep, stress, or a nutrient gap responds relatively quickly to the right intervention, usually within a few weeks. But fatigue that persists for more than six months, isn’t relieved by rest, and is accompanied by specific symptoms may indicate a condition called myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The defining features include fatigue so severe it limits your ability to work, socialize, or carry out daily activities, along with a worsening of symptoms after physical or mental exertion (sometimes appearing 12 to 48 hours later and lasting days or weeks), and sleep that doesn’t leave you feeling rested no matter how long you stay in bed.
Cognitive problems like difficulty concentrating and memory lapses, or symptoms that worsen when you stand or sit upright (dizziness, lightheadedness, increased fatigue), are additional markers. Thyroid disorders, sleep apnea, diabetes, anemia, and depression also cause persistent fatigue and are straightforward to screen for with blood work. If your fatigue doesn’t improve after addressing the basics, a blood panel checking ferritin, B12, vitamin D, thyroid function, and blood sugar is a practical next step.