Always Tired? Supplements for Energy That Are Worth Checking
Iron and B12 are the supplements worth checking when you are always tired. What helps, what does not (caffeine, CoQ10) and when to see a doctor.
7 min read
Supplements only tend to help tiredness when you're short of a nutrient. Iron and vitamin B12 are the two worth checking first, because low levels of either can cause fatigue, and a simple blood test can tell you. Extra B12 doesn't boost energy if your levels are already fine, and caffeine-based "energy" products only borrow energy. If you've been tired for weeks without a clear reason, see a doctor before buying anything.
Feeling tired all the time is one of the most common reasons people start taking supplements. Here is what's worth checking, what the evidence says about popular "energy" products and when tiredness needs a doctor rather than a pill.
Can supplements give you more energy?
Only if a deficiency is part of the problem. Most tiredness has everyday causes. The NHS lists not getting enough sleep, stress, depression, an unhealthy diet, not much exercise, hormonal changes and illnesses such as glandular fever or COVID-19[1]. No supplement fixes those.
Where supplements can make a real difference is in correcting a shortfall, such as low iron or low B12. The NHS says a GP may arrange blood tests to check for anaemia, diabetes or thyroid problems[1], which is why testing comes before buying. Our assistant can also explain a lab report in plain language; see below.
| Supplement | When it may help with tiredness | Check first |
|---|---|---|
| Iron | If you have iron deficiency or iron deficiency anaemia[2][3]. | Blood test first; some people absorb too much iron[3]. |
| Vitamin B12 | If you're deficient; no benefit for energy if levels are normal[4]. | Diet (vegan or vegetarian), age, metformin or acid-reducing medicines[4]. |
| Magnesium | Fatigue is an early sign of deficiency, but deficiency is uncommon in healthy people[5]. | Kidney disease; some antibiotics and osteoporosis medicines[5]. |
| Caffeine | Alertness, not a fix for the cause. | Up to 400 mg a day for most adults[6]. |
| CoQ10 | Not among the uses NCCIH reviews[7]. | Warfarin and insulin[7]. |
Could low iron be making you tired?
Yes, it's one of the most common nutritional causes of tiredness. The NHS lists tiredness and lack of energy, shortness of breath, heart palpitations, paler skin than usual and headaches as symptoms of iron deficiency anaemia, and says heavy periods and pregnancy are very common causes[2]. The NIH adds that women with heavy menstrual bleeding, pregnant women and frequent blood donors are among the groups most at risk[3], and that people who eat a vegetarian diet need 1.8 times as much iron, because iron from plant foods is absorbed less well[3].
Don't self-treat with iron. The NHS says to see a GP if you think you have iron deficiency anaemia; diagnosis is a simple blood test, and if you need iron tablets you'll usually take them for about 6 months, with follow-up tests[2]. Some people, such as those with hereditary haemochromatosis, absorb too much iron[3]. The adult upper limit is 45 mg a day, and doses of 45 mg or more can cause nausea and constipation[3]. Keep iron well away from children: accidental overdose is a leading cause of fatal poisoning in children under 6[3].
Vitamin C helps your body absorb iron from plant foods; see can I take iron and vitamin C together, and our iron guide.
Does vitamin B12 help with tiredness?
It helps if you're deficient; it doesn't add energy if your levels are already normal. B12 deficiency can cause fatigue, along with anaemia, palpitations, pale skin and numbness or tingling in the hands and feet, and the symptoms can take years to appear[4]. But the NIH says that despite B12's role in energy metabolism, supplements appear to have no benefit for performance in people without a deficiency[4].
The people most likely to be low are:
- Older adults, especially those with atrophic gastritis[4].
- People who follow vegetarian or vegan diets, because B12 is found naturally only in animal foods[4].
- People with pernicious anaemia, gut conditions or gut surgery[4].
- People taking metformin or acid-reducing medicines such as proton pump inhibitors long term[4].
The adult RDA is 2.4 micrograms a day, and no upper limit has been set because of B12's low potential for toxicity[4]. If you're in a group at risk, ask your doctor about testing. See our vitamin B12 guide.
What about magnesium for energy?
Only if you're low, which is uncommon in healthy people. The NIH lists fatigue and weakness, along with loss of appetite, nausea and vomiting, as early signs of magnesium deficiency, but says deficiency from diet alone is uncommon in otherwise healthy people because the kidneys hold on to magnesium[5]. Long-term use of some diuretics or proton pump inhibitors, digestive conditions such as Crohn's or coeliac disease, and alcohol dependence raise the risk[5].
The upper limit for magnesium from supplements is 350 mg a day for adults[5]. Read more in our magnesium guide.
Do caffeine pills and energy drinks work?
They make you feel more alert for a while, but they don't fix the reason you're tired, and they can disturb sleep. The FDA says 400 mg of caffeine a day is not generally associated with negative effects for most adults[6]. NCCIH says energy drinks contain about 70 to 240 mg of caffeine in a 16-ounce can and 113 to 200 mg in an energy shot, and that large amounts of caffeine may cause heart rhythm problems, anxiety, sleep problems and digestive problems[8]. Guarana contains caffeine too, so it adds to the total[8].
Avoid pure or highly concentrated caffeine powders: the FDA warns they can have serious consequences, including death, because a toxic amount is easy to mismeasure[6]. If you're pregnant, trying to conceive or breastfeeding, ask your doctor about caffeine limits[6]. The NHS also suggests avoiding caffeine in the couple of hours before bed[1].
Are CoQ10, ashwagandha and other "energy" supplements worth it?
The evidence for these as energy boosters is weak or missing. NCCIH's CoQ10 page doesn't cover energy or fatigue at all. For the uses it does review, the evidence doesn't support CoQ10 for statin-related muscle pain and is inconclusive for heart failure[7]. CoQ10 may interact with warfarin and insulin[7].
Ashwagandha is often marketed for energy, but NCCIH describes evidence for insomnia and stress rather than fatigue. It also notes rare liver injury, says to avoid it in pregnancy and breastfeeding, and says it isn't recommended for people with thyroid or autoimmune conditions[9].
When should you see a doctor about tiredness?
The NHS says to see a GP if you've felt tired for a few weeks and aren't sure why, if it's affecting your daily life, or if you have other symptoms such as weight loss or mood changes[1]. Tiredness with breathlessness, palpitations or pale skin is a reason to get checked for anaemia[2].
Meanwhile, the basics matter: aim for 6 to 9 hours of sleep at regular times, and don't drink too much alcohol[1].
How Suppin helps
- Once you allow AI, you can send the assistant a photo or PDF of a lab report, such as an iron or B12 test, and it explains it in plain language; nothing is stored.
- Your routine is built by fixed safety rules from your goals, diet, medications and conditions; nutrients that may interact aren't added automatically and show "Review with a professional".
- The Nutrients tab adds up iron, B12 and magnesium from all your products against daily values and upper limits.
- Reminders and a refill heads-up, so a course your doctor recommends doesn't lapse.
Get Suppin on the App Store, and read about the AI supplement assistant.
FAQ
There's no single best one. Iron and vitamin B12 are the most useful to check, because deficiency in either can cause fatigue[2][4], but they only help if you're actually low.
Not without a blood test. Tiredness can have many causes[1], and some people can build up too much iron[3]. A GP can check for iron deficiency anaemia with a simple blood test[2].
Only if you're deficient. The NIH says B12 supplements appear to have no benefit for performance in people with enough B12[4].
The FDA cites 400 mg a day as an amount not generally associated with negative effects for most adults[6]. People who are pregnant or sensitive to caffeine may need less.
Stress, low mood, diet, inactivity, hormonal changes and conditions such as anaemia or thyroid problems can all cause tiredness[1]. If it has lasted weeks, see a GP.
Sources
- NHS — Tiredness and fatigue
- NHS — Iron deficiency anaemia
- NIH Office of Dietary Supplements — Iron fact sheet
- NIH Office of Dietary Supplements — Vitamin B12 fact sheet
- NIH Office of Dietary Supplements — Magnesium fact sheet
- FDA — Spilling the beans: how much caffeine is too much?
- NCCIH — Coenzyme Q10
- NCCIH — Energy drinks
- NCCIH — Ashwagandha
Educational information, not medical advice. Check with your doctor or pharmacist before starting or changing supplements, especially if you take medication, are pregnant or have a health condition.
