Best Supplements for Energy and Fatigue: What Works in 2026

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

This guide breaks fatigue into three categories, matches each to the supplements with the strongest evidence, and explains exactly how they work so you can make an informed decision.

Why You Feel Tired: Three Types of Fatigue

Most fatigue falls into one of three broad categories, and understanding which one applies to you is the first step toward choosing the right supplement.

Nutrient-deficiency fatigue happens when your body lacks a vitamin or mineral it needs to produce energy or transport oxygen. Iron, vitamin B12, vitamin D and magnesium are the most common culprits. This type of fatigue tends to be constant rather than tied to specific situations, and it often comes with other signs like pale skin, muscle cramps or brain fog.

Stress-related fatigue is driven by prolonged activation of the hypothalamic-pituitary-adrenal (HPA) axis. When cortisol stays elevated for weeks or months, the body's energy regulation breaks down. You may feel wired but exhausted, sleep poorly despite being tired, or crash in the afternoon. Adaptogenic herbs target this pathway directly.

Mitochondrial fatigue relates to how efficiently your cells convert nutrients into ATP, the molecule that powers every process in the body. This type of fatigue is common in older adults, people recovering from illness, and anyone with a history of chronic tiredness that does not respond to rest alone.

Supplements for Nutrient-Deficiency Fatigue

Iron

Iron is essential for haemoglobin production. Without enough iron, your red blood cells cannot carry sufficient oxygen to your tissues, and the result is persistent tiredness, weakness and difficulty concentrating. Importantly, you do not need to be anaemic to experience iron-related fatigue. A 2017 meta-analysis in the British Journal of Nutrition found that iron supplementation significantly improved fatigue in people who were iron-deficient but not yet anaemic (Houston et al., 2017, DOI: 10.1017/S0007114517001015).

Iron deficiency is particularly common in women of reproductive age, vegetarians, and people with digestive conditions that impair absorption. If you suspect iron deficiency, ask your GP for a ferritin blood test before supplementing, as excess iron can be harmful. Our Iron Gummies with Vitamin C pair iron with vitamin C to support absorption.

Vitamin B12

Vitamin B12 is required for red blood cell formation and neurological function. Deficiency causes a type of anaemia that leads to extreme fatigue, weakness and cognitive difficulties. A 2021 systematic review in Nutrients confirmed that B12 supplementation is most effective in people with an actual deficiency rather than as a general energy booster (Markun et al., 2021, DOI: 10.3390/nu13030923).

Vegans, vegetarians, adults over 50 and anyone taking long-term acid-suppressing medications are at higher risk of B12 deficiency. Methylcobalamin is the active, bioavailable form of B12, meaning your body can use it directly without conversion. Our Vitamin B12 Methylcobalamin Capsules provide 1,000mcg per capsule in this preferred form.

Magnesium

Magnesium is involved in over 300 enzymatic reactions, including the conversion of food into ATP. Low magnesium impairs energy production at a cellular level, and symptoms include fatigue, muscle cramps and poor sleep. A landmark randomised controlled trial published in The Lancet found that magnesium supplementation significantly improved energy levels and reduced pain in patients with chronic fatigue (Cox et al., 1991, DOI: 10.1016/0140-6736(91)91371-Z).

Magnesium deficiency is common because modern diets are often low in magnesium-rich foods like dark leafy greens, nuts and seeds. Magnesium citrate is one of the better-absorbed forms. Our Magnesium Citrate 500mg Capsules provide a clinically relevant dose in an easily absorbed form.

Vitamin D

Vitamin D deficiency is widespread in the UK, particularly between October and March when UVB exposure is insufficient for skin synthesis. Low vitamin D has been consistently associated with fatigue, muscle weakness and low mood. The NHS recommends that all adults in the UK consider supplementing with vitamin D during autumn and winter, and people with darker skin or limited sun exposure may benefit year-round.

Vitamin D3 is the form your body produces naturally and is better absorbed than D2. Taking it alongside vitamin K2 helps direct calcium to bones rather than soft tissues. Our Vitamin D3 3000iu with Vitamin K2 combines both nutrients in a single capsule.

Supplements for Stress-Related Fatigue

When fatigue is driven by chronic stress rather than a nutrient gap, adaptogenic herbs offer a different approach. Adaptogens work by modulating the HPA axis, helping the body regulate its cortisol response rather than simply masking tiredness.

Ashwagandha

Ashwagandha (Withania somnifera) is the most extensively studied adaptogen for stress and fatigue. It reduces cortisol levels, supports GABA-mediated calming, and has been shown to improve both subjective energy and measurable stress markers. A double-blind, placebo-controlled trial found that 300mg of high-concentration ashwagandha root extract taken twice daily significantly reduced stress and anxiety scores while improving overall wellbeing (Chandrasekhar et al., 2012, DOI: 10.4103/0253-7176.106022).

KSM-66 is a patented full-spectrum ashwagandha extract standardised to a minimum 5% withanolides, which is the form used in most clinical trials. Our Ashwagandha KSM-66 Capsules provide 500mg per capsule of this clinically studied extract.

Rhodiola Rosea

Where ashwagandha excels at chronic stress, rhodiola rosea is particularly effective for acute mental fatigue, burnout and exhaustion. It works through different mechanisms, primarily by influencing serotonin and dopamine activity. A 2022 review in Molecules found that rhodiola preparations significantly improved all dimensions of chronic fatigue and burnout-related symptoms, including exhaustion, depression and insomnia (Ivanova Stojcheva and Quintela, 2022, DOI: 10.3390/molecules27123902).

If you are dealing with both chronic stress and acute burnout, combining ashwagandha and rhodiola covers both pathways. Our Shilajit Complex contains ashwagandha, rhodiola and shilajit together, making it a practical option if you want adaptogenic and mitochondrial support in a single supplement.

Supplements for Mitochondrial and Cellular Energy

If your fatigue persists despite adequate nutrition and manageable stress levels, the issue may lie at a cellular level. These supplements target mitochondrial function and ATP production directly.

Shilajit

Shilajit is a mineral-rich resin found in Himalayan rock formations. It contains fulvic acid, which acts as an electron carrier in mitochondria, supporting the efficiency of the electron transport chain where ATP is generated. A 2012 study in the Journal of Ethnopharmacology found that shilajit preserved mitochondrial membrane potential, stabilised complex enzyme activities and reversed oxidative stress markers in chronic fatigue models (Surapaneni et al., 2012, DOI: 10.1016/j.jep.2012.06.002).

Shilajit also enhances CoQ10 function, another key molecule in mitochondrial energy production. Our Shilajit Complex combines shilajit with ashwagandha and rhodiola, targeting both mitochondrial efficiency and stress-related fatigue in one formula.

Cordyceps

Cordyceps militaris is a functional mushroom with a long history of use for stamina and physical performance. Modern research suggests it works by increasing oxygen utilisation and supporting ATP production. A 2017 study in the Journal of Dietary Supplements found that cordyceps supplementation improved tolerance to high-intensity exercise, with participants showing significant improvements in time to exhaustion and VO2max after three weeks (Hirsch et al., 2017, DOI: 10.1080/19390211.2016.1203386).

Our Mushroom Complex includes cordyceps alongside lion's mane, reishi and chaga. If you are interested in cordyceps primarily for cognitive energy rather than physical performance, our standalone Lion's Mane Capsules focus specifically on nerve growth factor support and mental clarity.

Which Supplement Do You Need?

How to Choose the Right Supplement

Start with deficiencies. If you have not had blood work recently, ask your GP to check iron (ferritin), vitamin B12, vitamin D and magnesium levels. Correcting a genuine deficiency is the single most effective intervention for fatigue, and no adaptogen or mushroom supplement can compensate for a nutrient your body is missing.

Consider your stress levels. If your fatigue is clearly linked to a demanding period at work, poor sleep or emotional strain, an adaptogen like ashwagandha may help more than a multivitamin. KSM-66 ashwagandha has the strongest evidence base, and rhodiola is worth adding if mental exhaustion and burnout are prominent symptoms.

Layer if needed. These categories are not mutually exclusive. Someone who is both iron-deficient and chronically stressed might benefit from correcting the iron deficiency while also taking ashwagandha. The Shilajit Complex works well as an all-in-one for people who want adaptogenic and mitochondrial support without taking multiple separate supplements.

Give it time. Nutrient deficiencies typically take 4 to 8 weeks to correct. Adaptogens usually need 4 to 6 weeks of consistent use before the full effect is noticeable. If you see no improvement after 8 weeks, reassess with your GP rather than adding more supplements.

Important Considerations

Supplements work best as part of an overall approach to energy. Sleep quality, physical activity, hydration and a balanced diet all have a greater impact on energy levels than any supplement alone. If your fatigue is severe, sudden or accompanied by other symptoms like unexplained weight loss, it is important to see your GP to rule out underlying conditions such as thyroid disorders, diabetes or sleep apnoea.

Iron supplements should not be taken without confirming a deficiency through blood testing, as excess iron can accumulate and cause harm. Ashwagandha may interact with thyroid medications and immunosuppressants. If you are pregnant, breastfeeding or taking prescription medication, consult your healthcare provider before starting any new supplement.