Do energy supplements work? What causes fatigue and what helps

Usually not for the reason people buy them. Fatigue is a symptom, not a disease, and MedlinePlus lists dozens of possible causes, from poor sleep and stress to anemia, thyroid disease and depression. A supplement can only help if it fixes the specific thing that is draining you, and most "energy" bottles never say what that is. If you have felt tired for weeks, the useful first step is a conversation with a health care provider, not a new product.

Below is what the evidence says about the common energy ingredients (B vitamins, adaptogens, mitochondrial formulas), what causes tiredness in the first place, and how the energy offers we audited compare. This is general information, not medical advice.

What actually causes fatigue?

MedlinePlus defines fatigue as a feeling of weariness, tiredness or lack of energy, and says it can be a normal response to physical activity, emotional stress, boredom or lack of sleep. It also lists medical causes:

• Chronic diseases such as diabetes, COPD, and heart, liver, kidney and thyroid disease
• Anemia, infections, sleep apnea and other sleep disorders
• Depression and anxiety
• Treatments and medicines, including some antidepressants and antihistamines
• Habits: too little sleep, too much alcohol or caffeine, and too little or too much exercise

The same page says that if you have been tired for weeks, you should contact your provider, who can ask about sleep, activity and appetite, do an exam and order lab tests. That list is the reason an energy pill is a gamble: a formula built for one cause does nothing for the others, and some causes need real treatment.

Do B vitamins give you energy?

Only when you are short of them. Vitamin B12 is a good example. MedlinePlus explains that B12 helps form red blood cells and maintain the nervous system, that the body stores a few years' worth in the liver, and that low levels can cause anemia, weakness and numbness or tingling. Deficiency is most common in people over 50, people who follow a vegetarian or vegan diet, people who have had stomach or intestinal surgery, and people with conditions such as celiac disease, Crohn disease or pernicious anemia. For those groups, a provider may recommend a supplement. The adult recommended intake is 2.4 micrograms a day.

For everyone else, the evidence is thin. A 2021 systematic review and meta-analysis of 16 randomized trials with 6,276 participants looked at B12 (alone or with folic acid and B6) in people without overt deficiency. It found no effect on cognitive function and no overall effect on depressive symptoms. Only one study reported on fatigue, so the authors could not analyze it. In plain terms: the trials we have do not show that extra B12 lifts energy in people who are not deficient, and the one fatigue question has not been answered by enough studies.

Whether your B12 is low is something a blood test and a provider can tell you, and a bottle label cannot.

What about adaptogens like ashwagandha?

Adaptogens are herbs marketed for "stress resilience" and stamina. Ashwagandha is the best known. The NIH's National Center for Complementary and Integrative Health (NCCIH) says research suggests some ashwagandha preparations may help with insomnia and stress, while evidence on anxiety is unclear. It adds that many trials were small and used different preparations, and that there is not enough evidence to say it helps with conditions such as athletic performance or cognitive function. Fatigue is not on the list of things NCCIH says it supports.

NCCIH also gives safety points that sales pages seldom mention: ashwagandha may be safe for up to 3 months, long-term safety is unknown, rare cases of liver injury have been reported, and it can interact with medicines for diabetes, high blood pressure, thyroid conditions and sedatives. It should be avoided in pregnancy and by people with autoimmune or thyroid disorders. If you are on any of those medicines, ask a pharmacist before you buy.

Our Pineal 10X review shows how an adaptogen formula can go wrong. The liquid lists ashwagandha, maca, damiana, turmeric and iodine, but not a single amount, and our review notes iodine has a narrow safe intake range, so an unstated dose is a real concern. The pitch built on "activating" the pineal gland has no clinical basis, and checkout adds a $7.99 monthly digital add-on that bills automatically.

Do mitochondrial and "cellular energy" formulas work?

These products borrow the language of cell biology: ingredients such as CoQ10, PQQ and acetyl-L-carnitine are described as fuel for mitochondria. The honest question is dose. The Advanced Mitochondrial Formula review credits the offer for printing an amount for all 10 ingredients and for disclosing that its formulator is paid. But it finds that several doses (CoQ10 at 50 mg, PQQ at 5 mg, acetyl-L-carnitine at 190 mg, resveratrol at 25 mg) are well below the amounts used in the human trials usually cited for those ingredients. That makes the real-world result harder to predict than the sales page implies.

A formula with a full label is a better starting point than one with a hidden blend, because you can at least check it. It still does not prove that it will make you feel less tired.

How do offers with a hidden label score?

At the other end are offers that tell you almost nothing. The KundaliniFlow review found no ingredient names, amounts or Supplement Facts panel on the sales page, the checkout or the terms page, and its own terms say the name attached to the product is a pseudonym. The Nervolink review found a mushroom blend where four of nine ingredients carry a stated 266 mg amount, but five sit in an undisclosed blend, and the one relevant nerve study it could find was done in injured rats, not people.

These are different problems with the same effect: you cannot compare what is in the capsule to any study, so you cannot judge whether it could plausibly do what the page implies. Our scoring method treats a blank or blended label as a transparency penalty for exactly that reason.

What about energy ebooks?

Not every energy offer is a capsule. Two ebooks we reviewed handle the medical side poorly. The Energy and Fatigue Recovery Guide for Women is a $37 one-time ebook on food, sleep, movement and stress, topics that are ordinary and harmless, but its page never tells readers to get persistent tiredness checked, and it names no author. From Fatigue to Fit treats tiredness as a food problem, and our review flags that persistent tiredness has medical causes a meal plan will not find. For low-cost lifestyle advice that is a small risk, but it is a poor answer to unexplained fatigue.

A practical checklist for tired days

1. Note how long you have felt tired. MedlinePlus says to call your provider if it lasts for weeks.
2. Keep a fatigue diary for a week or two. MedlinePlus suggests it can show patterns in when you feel more tired or have more energy.
3. Work on the basics it lists: regular physical activity, better sleep habits, stress management, a healthy diet and limited alcohol and caffeine.
4. Ask for lab tests if your provider thinks they are warranted. Do not self-diagnose with a supplement.
5. Before buying a product, check for a Supplement Facts panel with amounts, the study behind each claim, and the checkout page for add-ons and subscriptions.
6. Tell your pharmacist about every herb you take, especially ashwagandha, because of medicine interactions.
7. Browse the energy and wellness category to compare offers side by side.

FAQ

Why am I always tired even though I sleep enough?

Many things can cause it besides sleep time: anemia, thyroid problems, sleep apnea, depression, medicines and stress are all on the MedlinePlus list. If it lasts for weeks, see a provider who can order tests. A supplement cannot sort out which of these applies.

Do energy supplements work?

It depends on the ingredient and the person. B12 matters if you are deficient, but trials in people who are not deficient did not show an overall effect on depression or cognition, and fatigue was not analyzable. Adaptogens such as ashwagandha have some evidence for stress and sleep, not clearly for fatigue. Ask a clinician before relying on any of them.

Is it safe to take ashwagandha every day?

NCCIH says it may be safe in the short term, up to 3 months, and that long-term safety is unknown. Rare liver injury has been reported, and it can interact with several medicines. Check with a doctor or pharmacist first.

Can a supplement replace a doctor visit for fatigue?

No. Fatigue can be the first sign of a medical condition, and MedlinePlus advises contacting a provider when it lasts for weeks. A product marketed for energy is not a diagnosis.