Best Supplements for Energy and Fatigue: What Works in 2026

Persistent tiredness is one of the most common health complaints in the UK, and there is no single supplement that fixes every type of fatigue. The right choice depends on why you are tired, because nutrient deficiency, chronic stress and poor mitochondrial energy production each call for different interventions.

This UK guide groups fatigue into three categories, matches each to the supplements with the strongest evidence, and tells you when a blood test or a GP visit should come before any supplement at all.

Why You Feel Tired: Three Types of Fatigue

Fatigue is a symptom, not a diagnosis. The same tiredness can come from a missing nutrient, a stressed-out nervous system, or poor cellular energy production, and the supplement that helps one type may do nothing for the other two.

The simplest filter is to start with the most common cause in your situation. Women of reproductive age and vegans are most likely to be in the nutrient-deficiency group, anyone working through prolonged work or sleep pressure tends to fit the stress group, and people over 50 or training hard often fall into the mitochondrial group.

The table below uses your main symptom to suggest where to begin.

Supplements for Nutrient-Deficiency Fatigue

This is the group where supplements have the clearest impact, because correcting a real deficiency directly fixes the cause of the tiredness. None of the four nutrients below should be supplemented at high doses without first knowing your blood levels, particularly iron.

Iron

Iron deficiency is the most common nutritional deficiency in the UK and a major hidden cause of fatigue in menstruating women. Low iron means less haemoglobin, which means less oxygen reaching your muscles and brain.

Always confirm iron deficiency with a ferritin blood test before supplementing. Our guide to the best iron supplements for women in the UK covers the forms with the lowest side-effect profile and how to take them so you actually absorb the dose.

Vitamin B12

B12 deficiency causes fatigue, low mood, brain fog and tingling in the hands and feet. Vegans, vegetarians, people over 50 and anyone on long-term acid-blocking medication are at highest risk, because B12 only occurs naturally in animal foods and needs stomach acid to be absorbed.

Methylcobalamin is the body-ready form and the better choice for most people. A 1000 microgram daily dose is well above the NHS recommended intake and is commonly used to top up a low level over weeks to months.

Magnesium

Magnesium is involved in more than 300 enzymatic reactions including the production of ATP, the body's main energy currency. A real magnesium gap can show up as cramps, poor sleep, irritability and a tired-but-wired feeling rather than the heavy tiredness of iron or B12 deficiency.

Citrate is the best general-purpose form and is well absorbed. Glycinate is the calming form and the better choice for anyone whose tiredness is intertwined with poor sleep.

Vitamin D

Vitamin D supports immune function, mood and musculoskeletal health, all of which influence how energetic you feel. The NHS advises that adults in the UK consider a daily supplement of 10 micrograms (400 IU) in autumn and winter, with higher strengths used to correct documented low levels under guidance.

Take vitamin D with your largest meal, because it is fat-soluble. For more on dose strength see our UK vitamin D dosage guide.

Supplements for Stress-Related Fatigue

If your bloods look normal but you still feel exhausted, the most likely culprit is chronic stress on your nervous system. Adaptogenic herbs like ashwagandha and rhodiola work by helping the body manage its stress response rather than by stimulating you, which is why they suit the tired-but-wired pattern.

Ashwagandha

Ashwagandha has the strongest clinical evidence among adaptogens for chronic stress and fatigue. It lowers cortisol and supports the hypothalamic-pituitary-adrenal axis that controls how the body reacts to ongoing pressure.

Most trials use the KSM-66 extract at 300 to 600mg daily, taken consistently for 8 to 12 weeks. People with thyroid conditions or autoimmune disorders should check with a GP before starting.

Rhodiola Rosea

Rhodiola suits acute mental fatigue, burnout and the kind of exhaustion that follows a busy or stressful period. It acts on serotonin and dopamine pathways and tends to feel slightly stimulating, which is why it is often taken in the morning rather than the evening.

For a head-to-head between the two adaptogens see our ashwagandha vs rhodiola guide. Many people use both, since they cover different stress patterns.

Supplements for Mitochondrial and Cellular Energy

Mitochondria are the energy producers inside every cell. When they work poorly, you can have normal bloods and a calm nervous system and still feel flat, particularly during physical effort.

Shilajit

Shilajit is a mineral-rich resin used in Ayurvedic medicine and now backed by a small but growing modern evidence base. Its main active fulvic acid supports mitochondrial ATP production and may reduce perceived fatigue, which is why it has become a popular pick for over-40 men.

A 2012 study in CFS-prone men found that 200mg of purified shilajit daily for 8 weeks improved mitochondrial function and reduced fatigue scores (Surapaneni et al., 2012, DOI: 10.1016/j.jep.2012.03.024). Quality and purification matter, so look for products that list the source and processing.

Cordyceps

Cordyceps is the mushroom most often linked to physical energy and exercise endurance. A 2017 trial reported improvements in time to exhaustion and VO2max with three weeks of cordyceps-based supplementation in healthy adults (Hirsch et al., 2017, DOI: 10.1186/s12970-017-0181-z).

It is most commonly taken in combination products alongside other functional mushrooms like reishi and lion's mane. Plan to stay on it for at least 4 to 6 weeks before judging whether it is helping.

Stacking Supplements: What Goes With What

Some pairings work harder than others. Iron and vitamin C taken together improve iron absorption, while iron and tea or coffee taken at the same time blunt it, so anyone supplementing iron should keep their morning tea at least an hour away from their dose.

Vitamin D pairs naturally with magnesium, since magnesium activates the enzymes that convert vitamin D into its usable form. The table below shows the most useful daily pairings and the timings that go with them.

How to Choose the Right Supplement

Start with the most likely cause, not the supplement with the loudest marketing. The single most useful step for energy-related fatigue is a blood test that covers ferritin, vitamin B12, vitamin D and full blood count, because correcting a real deficiency is the highest leverage move you can make.

If your bloods are clean, the next question is whether your tiredness is more anxious-and-wired or more flat-and-burned-out. Anxious-and-wired points to ashwagandha; flat-and-burned-out points to rhodiola; tired in physical effort points to shilajit or cordyceps.

Avoid stacking five or six new supplements at once. You will not know which one is helping, and you will not catch a side effect cleanly. Add one ingredient, give it 6 to 8 weeks, and judge from there.

What About Caffeine and Energy Drinks?

Caffeine masks tiredness rather than fixing it. It blocks adenosine receptors that signal fatigue, which is why a coffee feels like an energy boost even when the underlying cause of your tiredness is unchanged.

For most adults, up to 400mg of caffeine a day is considered safe, roughly four mugs of instant coffee. Energy drinks add taurine, B vitamins and large amounts of sugar, but none of those ingredients fix nutrient deficiencies, stress, or poor mitochondrial function.

If you find yourself relying on three or more coffees a day to function, treat that as a symptom worth investigating rather than the answer.

Important Considerations

Supplements are not a substitute for a GP visit. If your fatigue is new, severe, or accompanied by other symptoms like unexplained weight loss, persistent breathlessness or low mood, see your GP first, because the cause may be a thyroid issue, anaemia, sleep disorder or something else that needs proper investigation.

Speak to your GP or pharmacist before starting new supplements if you are pregnant, breastfeeding, taking prescription medication, or managing a long-term condition. Ashwagandha can affect thyroid function and should be approached carefully if you have a thyroid disorder.

When a Supplement Is Not Enough

Some patterns of fatigue need investigation rather than a new capsule. If your tiredness is severe, has come on suddenly, or has lasted more than a few weeks despite reasonable sleep, that warrants a GP appointment before anything else.

Common medical causes the NHS looks for include iron-deficiency anaemia, vitamin B12 deficiency, hypothyroidism, sleep apnoea, type 2 diabetes and depression. A blood panel covering ferritin, full blood count, B12, vitamin D and thyroid function is a standard first step.

Once any medical cause is ruled out or treated, the supplement framework in this guide can support recovery alongside the basics of sleep, food and movement.

Frequently Asked Questions