Iron vs Vitamin D for energy
Short answer: For energy, users rate them about the same: 88% report improvement with Iron (49 reports) and 87% with Vitamin D (255 reports).
Iron has 243 meta-analyses and 693 randomized trials on PubMed; Vitamin D has 3,251 and 4,560.
Based on 252 reports about Iron and 3,058 about Vitamin D. Not medical advice.
| Iron Supplement | Vitamin D Supplement | |
|---|---|---|
| Users say it helped | 69%helped88 reports · medium confidence | 67%helped1,101 reports · high confidence |
| Verdict | Mostly positive | Mostly positive |
| Research | AResearch: Strong | AResearch: Strong |
| Meta-analyses / RCTs | 243 / 693 | 3,251 / 4,560 |
| Mainly used for | ||
| Mood % reporting improvement | 100% (8) | 88% (393) |
| Energy % reporting improvement | 88% (49) | 87% (255) |
| Sleep % reporting improvement | 100% (2) | 52% (119) |
| Immunity % reporting improvement | — | 98% (94) |
| Anxiety % reporting improvement | 100% (3) | 64% (90) |
| Common side effects | stomach issues, liver accumulation, overdose toxicity, iron overload | insomnia, anxiety, hypercalcemia, nausea |
| Typical dose reported | 65 mg | 10,000-20,000 IU / daily |
High-level ID female athletes experience a negative impact on endurance performance, which can be improved by supplementing with ∼100 mg of elemental iron per day or bi-daily. The decrements in other performance parameters characterizing a range of sports coincide with the severity of iron deficiency.
J Sport Health Sci, 2025 ↗“I supplemented with sublingual b12 and iron and daily electrolytes and I'm feeling much better.”
These results indicate that the prevalence of vitamin D deficiency was more elevated in obese subjects. The vitamin D deficiency was associated with obesity irrespective of age, latitude, cut-offs to define vitamin D deficiency and the Human Development Index of the study location.
Obes Rev, 2015 ↗“First thing I noticed was my mood & libido, I have more 'feeling/sensitivity' down there.”
Related comparisons
Percentages come from first-hand user reports and are not clinical outcomes. Talk to a doctor before starting, stopping or combining anything. How we rate