Iron
Contributes to normal formation of red blood cells and haemoglobin, and to the normal transport of oxygen in the body.
Also known as Iron Bisglycinate, Ferrous Sulfate, Ferrous Fumarate, Iron Supplement, Ferrous Gluconate
Common doses
18-65 mg
Best timing
Morning
Food
Take on an empty stomach
Interactions
11 known
Iron is an essential mineral required for oxygen transport, energy production, and DNA synthesis. It is a core component of haemoglobin (which carries oxygen in red blood cells) and myoglobin (which stores oxygen in muscles). Iron deficiency is the most common nutritional deficiency worldwide, affecting approximately 1.6 billion people.
Iron deficiency is particularly prevalent in women of reproductive age, endurance athletes, vegetarians, and frequent blood donors. The body has no regulated mechanism for excreting excess iron, which is why iron supplementation should be guided by blood work. Too much iron (haemochromatosis) is as dangerous as too little.
Iron absorption is heavily influenced by what you take it with. Vitamin C dramatically enhances absorption, while calcium, tannins (tea/coffee), and phytates (grains) inhibit it. This makes timing and food pairing critical for iron supplementation.
Key benefits
Oxygen transport
Iron contributes to normal formation of red blood cells and haemoglobin, and to normal oxygen transport in the body.
Energy and fatigue
Iron contributes to the reduction of tiredness and fatigue. Iron-deficiency anaemia is one of the most common causes of chronic fatigue.
Cognitive function
Iron contributes to normal cognitive function. The brain consumes 20% of the body's oxygen, making it particularly sensitive to iron status.
Immune function
Iron contributes to the normal function of the immune system. Iron-deficient individuals are more susceptible to infections.
Available forms
Ferrous Bisglycinate
Chelated iron. Best absorbed, gentlest on the stomach. Preferred for supplementation. More expensive but fewer GI side effects.
Ferrous Sulfate
The most commonly prescribed form. Effective but can cause nausea, constipation, and stomach upset. Take on an empty stomach.
Ferrous Fumarate
Contains more elemental iron per tablet. Similar absorption to ferrous sulfate with comparable GI side effects.
Iron Polysaccharide Complex
Gentler on the stomach. Lower absorption rates but better tolerated. Often recommended when ferrous forms cause GI issues.
Food sources
- Red meat (beef, lamb)
- Liver and organ meats
- Shellfish (oysters, clams)
- Spinach and dark leafy greens
- Legumes (lentils, chickpeas)
- Fortified cereals
Signs of deficiency
- Fatigue and weakness
- Pale skin and nail beds
- Shortness of breath
- Cold hands and feet
- Brittle nails (spoon-shaped)
- Restless leg syndrome
- Unusual cravings (ice, dirt)
Upper intake limit
45 mg/day elemental iron (NIH). Only supplement iron if blood work confirms deficiency or insufficiency. Excess iron is stored and can cause organ damage.
Research summary
Strong evidence for treating iron-deficiency anaemia and improving fatigue in iron-depleted individuals. Important: iron is one supplement that should be guided by blood work (serum ferritin, transferrin saturation). Supplementing without confirmed deficiency is not recommended due to the risks of iron overload.
Known interactions (11)
Calcium blocks iron absorption significantly
Iron and zinc compete for absorption
Iron and manganese share the same transporter
Green tea sharply reduces iron absorption
Curcumin chelates iron
Possible absorption competition
Coffee polyphenols sharply reduce iron absorption
L-DOPA chelates iron, reducing absorption of both
Glucomannan's gel traps iron in the gut
Vitamin C boosts iron absorption
Copper is required for iron metabolism
Check your full stack
for interactions.
See what competes, what combines well, and when to take everything. Every interaction cites a published source.
Stack
6 supplements
Stack review
1 flagZinc and Iron compete for the same absorption pathway. Take at least 2 hours apart.
Supplements
This information is for educational purposes only. It is not medical advice and does not diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional.