Iron
Also known as Ferrous bisglycinate, Ferrous sulfate
Iron is the core of hemoglobin, which carries oxygen through the blood. Deficiency causes fatigue and is especially common in menstruating women, vegetarians, and endurance athletes — but iron should only be supplemented when low.
Benefits
Corrects iron-deficiency fatigue
StrongRestoring iron stores resolves the tiredness of deficiency anemia.
Supports exercise capacity
ModerateAdequate iron is needed for oxygen delivery during exertion.
Pros & cons
Pros
- Resolves a very common deficiency
- Dramatic energy improvement when deficient
Cons
- Constipating for many people
- Dangerous if taken without deficiency
Side effects
Constipation and GI upset
A very common reason people stop iron; gentler forms or alternate-day dosing help.
Toxic in overload
Excess iron is harmful — never supplement without confirmed need.
How to take it
Typical dose
Only when deficient; commonly 18–65 mg elemental iron
Timing
With vitamin C; away from calcium, coffee, and tea
Common forms
Tip: Alternate-day dosing can improve absorption and reduce side effects.
What the research says
Iron and fatigue in deficiency
StrongSupplementation improves fatigue and work capacity in iron-deficient individuals, even without full anemia.
Alternate-day iron dosing
ModerateSpacing doses may increase fractional absorption by reducing hepcidin spikes.
How it connects
Relationships between Iron and other supplements in the matrix.
Vitamin C strongly increases absorption of plant-based iron when taken together.
Compare the pairingCalcium taken at the same time inhibits iron absorption — separate them by at least two hours.
Compare the pairingImportant cautions
- Do not supplement iron without a blood test confirming deficiency. Keep away from children — overdose is dangerous.