Energy depletion affects millions of people globally, whether from intense physical training, chronic fatigue conditions, mental demands, or simply the wear of daily life. While proper sleep, nutrition, and exercise form the foundation of sustained energy, certain supplements have demonstrated measurable improvements in objective performance metrics and subjective fatigue ratings across rigorous clinical trials.
The supplement landscape is cluttered with bold marketing claims, but evidence-based rankings help distinguish genuinely effective interventions from overhyped products. This guide ranks energy-supporting supplements by the strength and consistency of human clinical evidence, incorporating effect sizes, sample sizes, and replication across independent research groups.
Supplements in this guide are classified into tiers based on the quantity and quality of human clinical evidence:
- Tier 4 (Strongest Evidence): Multiple well-designed RCTs with large sample sizes, consistent positive outcomes, and clinically meaningful effects across independent research groups.
- Tier 3 (Probable Efficacy): Multiple RCTs with positive outcomes, but limited by smaller sample sizes, shorter durations, or inconsistent results across studies.
- Tier 2-1 (Weaker Evidence): Limited human data, primarily animal studies, or mixed/negative human RCT results.
What It Is: A naturally occurring compound synthesized from amino acids in the liver and kidneys. Creatine functions as a rapid energy buffer in muscle cells, regenerating ATP (the primary cellular energy currency) during high-intensity activity.
The Evidence: Creatine monohydrate boasts the most consistent evidence base for energy-dependent performance. Multiple large, well-designed RCTs demonstrate clinically meaningful improvements in power output, strength, and repeated-sprint performance—exactly the scenarios where energy availability becomes limiting.
A landmark human RCT (n=31) showed creatine loading increased muscle total creatine concentration by approximately 20% within just 6 days of 20 g/day supplementation, with levels maintained at 2 g/day thereafter. In elite youth soccer players, 14 days of low-dose creatine supplementation (0.03 g·kg/day) significantly increased peak power output and mean power output on Wingate testing, with p-values ≤0.05.
The effects are particularly pronounced during high-intensity, short-duration activities—the exact energetic scenarios where phosphocreatine depletion limits performance.
Dosing: 3-5g once daily (oral)
Cost: $8-$25/month
Best For: Athletes engaged in high-intensity interval training, strength sports, repeated-sprint activities, and anyone seeking objective improvements in power output and work capacity.
What It Is: An essential mineral central to oxygen transport, cellular respiration, and ATP production. Iron forms the core of hemoglobin (oxygen carrier) and myoglobin (muscle oxygen storage) while supporting dozens of energy-metabolism enzymes.
The Evidence: Iron supplementation demonstrates strong evidence for improving energy-related outcomes specifically in iron-deficient individuals. The efficacy is particularly pronounced in those with documented iron deficiency, though benefits extend to non-anemic populations with depleted iron stores.
A comprehensive meta-analysis examining iron supplementation effects on fatigue (n=1,408) found effect sizes of d=0.34 in RCTs and d=1.01 in pre-post studies. In female athletes with iron deficiency, endurance performance improved 2-20% and maximal aerobic capacity improved 6-15% with 16-100 mg/day elemental iron supplemented for 16-56 days (meta-analysis, n=669).
The mechanism is straightforward: restoring iron levels increases hemoglobin and myoglobin, enhancing oxygen availability for aerobic energy production.
Dosing: 25-36mg elemental iron once daily (oral)
Cost: $8-$30/month
Best For: Individuals with documented iron deficiency, female athletes, vegetarians, and anyone experiencing fatigue accompanied by low iron markers (serum ferritin, transferrin saturation).
What It Is: An adaptogenic herb from traditional Ayurvedic medicine containing withanolides—bioactive compounds that modulate stress response and support cognitive function.
The Evidence: Ashwagandha shows consistent positive effects on cognitive energy and mental fatigue across multiple RCTs, though sample sizes remain modest and standardization varies between products.
In one RCT (n=120), ashwagandha 600 mg/day improved working memory, episodic memory, and attention on cognitive testing with significant improvements in mood vigor and mental fatigue reduction versus placebo over 8 weeks. A separate trial (n=overweight/obese adults) found statistically significant reduction in fatigue symptoms on the Chalder Fatigue Scale with ashwagandha 400 mg/day versus placebo (p=0.016) over 12 weeks.
The evidence is strongest for mental/cognitive fatigue rather than physical energy depletion, distinguishing it from creatine or iron.
Dosing: 300-600mg once daily or split into two doses (oral)
Cost: $15-$45/month
Best For: Individuals experiencing mental fatigue, cognitive fog, stress-related tiredness, and those seeking adaptogenic support without stimulant effects.
What It Is: An essential mineral required for ATP synthesis, energy metabolism, and muscle relaxation. Magnesium functions as a cofactor in over 300 enzymatic reactions.
The Evidence: Magnesium shows mixed evidence for energy outcomes. Some RCTs report improvements in fatigue perception and recovery, while others show negligible or even detrimental effects on objective performance.
In fibromyalgia patients (n=89, double-blind RCT), fatigue improved significantly in the placebo group but showed non-significant reduction with magnesium supplementation, though sleep quality and functional impact improved. Conversely, in volleyball players (n=25, 4-week RCT, 350 mg/day), magnesium supplementation decreased lactate production and increased countermovement jump height by up to 3 cm compared to control.
Magnesium appears most beneficial for exercise recovery and muscle function rather than direct energy augmentation.
Dosing: 200-400mg elemental magnesium once daily (oral)
Cost: $12-$45/month
Best For: Athletes, individuals with documented magnesium deficiency, and those seeking post-exercise recovery support.
What It Is: A fat-soluble steroid hormone synthesized in skin upon sunlight exposure. Vitamin D regulates calcium homeostasis, immune function, and influences hundreds of genes including those involved in energy metabolism.
The Evidence: Vitamin D3 supplementation shows probable efficacy for improving energy and reducing fatigue in deficient individuals, supported by multiple RCTs and meta-analyses.
A double-blind RCT (n=120) found the Fatigue Assessment Scale decreased significantly more in the vitamin D group versus placebo (−3.3 ± 5.3 vs −0.8 ± 5.3, P=0.01). Notably, 72% of vitamin D-supplemented participants reported fatigue improvement versus 50% in placebo (OR 2.63, 95% CI 1.23–5.62).
Effects are strongest in deficient individuals, with minimal benefits for those maintaining adequate serum 25-hydroxyvitamin D levels.
Dosing: 2,000-5,000 IU once daily (oral)
Cost: $5-$20/month
Best For: Individuals with documented vitamin D deficiency, those with limited sun exposure, and anyone experiencing fatigue accompanied by low vitamin D levels.
What It Is: An essential trace mineral supporting immune function, protein synthesis, and enzyme activity. Zinc participates in energy metabolism through multiple pathways.
The Evidence: Zinc shows probable efficacy for reducing fatigue in elderly populations and cancer patients, with consistent results across 2-3 RCTs. Sample sizes remain small, but effects are consistent.
In one RCT, zinc supplementation (30 mg/day × 70 days) significantly reduced fatigue in the elderly (n=150): mean fatigue score difference −10.41 versus +1.37 in control (P<0.001) with increased serum zinc (14.22 μg/dL versus −0.57 in control). Cancer patients on chemotherapy (70 mg/day zinc × 16 weeks) maintained quality of life and fatigue scores; the placebo group showed significant worsening between treatment cycles.
Dosing: 15-30mg elemental zinc once daily (oral)
Cost: $8-$25/month
Best For: Elderly individuals, cancer patients undergoing chemotherapy, and those with documented zinc deficiency.
What It Is: The primary bioactive compound in turmeric with potent anti-inflammatory and antioxidant properties. Curcumin modulates cellular signaling involved in energy production and exercise recovery.
The Evidence: Curcumin shows probable but inconsistent efficacy for energy and fatigue, with most positive evidence emerging from exercise recovery contexts.
In exhaustive swimming mice, curcumin (100 mg/kg) increased swimming time by 273.5% versus control and reduced blood ammonia by 21%, lactic acid by 18.6%, and lactate dehydrogenase by 21.9%. In humans, postmenopausal women (n=64, RCT) receiving curcumin 500mg twice daily for 8 weeks showed significantly reduced fatigue scores compared to placebo (p<0.05).
However, findings are not universally replicated, limiting confidence.
Dosing: 500-1,000mg twice daily (oral)
Cost: $10-$55/month
Best For: Individuals engaging in intense exercise, those with inflammatory conditions, and those seeking antioxidant support during demanding physical training.
What It Is: A flavonoid antioxidant abundant in plant foods with immunomodulatory and mitochondrial-supporting properties.
The Evidence: Quercetin shows moderate evidence for improving energy and exercise performance, with consistent benefits for fatigue reduction in some studies but mixed results in others.
In a double-blind RCT (n=78), 500 mg quercetin daily for 2 months reduced Fatigue Impact Scale scores by 10.6 points versus placebo in healthy adults. Seven days of 1,000 mg/day quercetin increased cycling time-to-exhaustion by 13.2% and VO2max by 3.9% versus placebo in untrained adults (n=12, RCT).
However, several high-quality studies show null or negative results, indicating quercetin's effects are conditional and population-dependent.
Dosing: 500-1,000mg once to twice daily (oral)
Cost: $15-$60/month
Best For: Endurance athletes, individuals experiencing chronic fatigue, and those seeking antioxidant support during training.
What It Is: A polyphenol found in red grapes, berries, and other plants that activates mitochondrial biogenesis pathways and supports cellular energy production.
The Evidence: Resveratrol shows probable efficacy for energy metabolism, with multiple RCTs demonstrating improvements in mitochondrial function and metabolic markers.
In trained individuals, mitochondrial capacity increased approximately 40% with resveratrol+piperine versus approximately 10% with placebo after 4 weeks of exercise training (n=16, RCT, p=0.02). Thirty-day resveratrol supplementation (150 mg/day) reduced resting metabolic rate, increased AMPK activation and citrate synthase activity, improved muscle mitochondrial respiration on fatty acid substrate, and decreased inflammatory markers in obese men (n=11, RCT).
Dosing: 250-500mg once daily (oral)
Cost: $10-$45/month
Best For: Individuals seeking mitochondrial support, those with metabolic challenges, and trained athletes focused on recovery optimization.
What It Is: A nucleotide precursor to NAD+, a coenzyme essential for cellular energy production, DNA repair, and mitochondrial function.
The Evidence: NMN demonstrates probable efficacy for energy-related outcomes in humans, with multiple RCTs showing improvements in physical performance, aerobic capacity, and fatigue reduction.
In older Japanese adults (n=108, 12-week RCT, 250 mg/day), NMN improved 5-times sit-to-stand performance with effect size d=0.72 and reduced drowsiness (d=0.64). In amateur runners, VO2max and power at ventilatory thresholds increased significantly over 6 weeks with 300-1,200 mg/day NMN supplementation combined with exercise training (n=48).
Dosing: 250-500mg once daily (oral)
Cost: $25-$80/month
Best For: Aging populations, endurance athletes, and those seeking mitochondrial age-reversal support.
What It Is: Hydrolyzed collagen providing amino acids, particularly glycine, proline, and hydroxyproline that support joint health, recovery, and potentially endurance capacity.
The Evidence: Collagen peptides show probable benefits for energy-related outcomes including reduced fatigue perception, improved post-exercise recovery, and enhanced endurance capacity.
Healthy adults (n=31 per group, RCT) receiving 10g/day collagen peptides for 8 weeks showed reduced fatigue perception (T-score Fatigue-Inertias: 47.0 ± 7.4 versus 51.5 ± 9.0, p=0.045) and increased vigor (T-score: 53.9 ± 10.7 versus 47.3 ± 9.6, p=0.002). In moderately trained males, 15g/day collagen peptides combined with training improved running endurance performance: 1,727 ± 705m greater distance in 1-hour time trial versus placebo 1,018 ± 976m (p≤0.05) over 12 weeks (n=32, RCT).
Dosing: 10-20g once daily (oral)
Cost: $20-$60/month
Best For: Endurance athletes, individuals seeking recovery support, and those concerned with joint health alongside energy.
What It Is: Beneficial live microorganisms that support gut microbiota composition, intestinal barrier function, and immune signaling—all relevant to energy metabolism.
The Evidence: Probiotics show probable benefits for energy and fatigue in athletes and disease populations, though efficacy is not conclusively proven.
Cyclists supplemented with multi-strain probiotics for 4 months showed increased maximal oxygen uptake from 65.28 to 69.18 mL/kg/min, prolonged exercise duration by approximately 1.3 minutes, and reduced perceived exertion (Borg scale 19.38 versus 18.43) versus placebo (n=26, RCT). Multiple sclerosis patients given Saccharomyces boulardii for 4 months showed significant reduction in fatigue severity (p=0.01) and pain intensity (p=0.004) versus placebo with improved quality of life scores (n=40, RCT).
Dosing: 10-100 billion CFU once daily (oral)
Cost: $15-$80/month
Best For: Athletes, disease populations with fatigue components (MS, autoimmune conditions), and those seeking gut-energy optimization.
What It Is: A neurotransmitter and antioxidant primarily known for circadian rhythm regulation but also involved in mitochondrial function and exercise recovery.
The Evidence: Melatonin shows moderate evidence for improving energy and fatigue in specific populations, with consistent positive findings in cancer-related fatigue and post-exercise contexts.
A meta-analysis of cancer-related fatigue (9 RCTs) found melatonin improved fatigue versus placebo (SMD: −0.23, 95% CI: −0.44 to −0.01, p=0.04), with significant effects only at ≥13 weeks treatment duration (SMD: −0.38). In trained males (n=12, RCT), 6 mg melatonin improved 5-meter shuttle run total distance, fatigue index, and sprint decrement percentage (all p<0.05) with enhanced perceived recovery status up to 72 hours post-exercise.
Dosing: 0.5-5mg once daily (oral)
Cost: $4-$20/month
Best For: Cancer patients experiencing treatment-related fatigue, athletes seeking recovery optimization, and those with circadian misalignment.
What It Is: A traditional Southeast Asian herb containing bioactive compounds that may support testosterone synthesis and stress resilience through cortisol modulation.
The Evidence: Tongkat Ali shows probable efficacy for improving energy and fatigue in humans based on 4 RCTs