How to Choose the Right Iron Supplement

Iron deficiency is one of the most common nutrient deficiencies affecting women, especially those with heavy menstrual bleeding, perimenopausal cycle changes, or following pregnancy. If you’ve searched “best iron supplement for women” or “how to choose iron supplement,” you’re not alone — the answer isn’t one-size-fits-all. Different iron supplements contain different forms and amounts of iron, and they affect the body—and the gut—differently.

What Is Iron — and Why Does It Matter?

Iron is a mineral your body needs to:

• Carry oxygen in your blood
• Make energy
• Support brain function
• Maintain hair, skin, and nails
• Support the immune system

When iron levels are low, your body struggles to deliver oxygen efficiently. Iron deficiency can cause:

• Fatigue
• Cold intolerance
• Shortness of breath with activity
• Hair loss/shedding
• Headaches
• Restless legs
• Reduced exercise tolerance
• Irritability
• Pica (cravings for non-food items such as ice, clay, or dirt) (BC Guidelines, 2019)

Iron Deficiency vs. Anemia: What’s the Difference?

These terms are often used interchangeably, but they describe different stages of the same problem.

Iron deficiency means your body’s iron stores are low. This often develops first and may not show up on a standard complete blood count (CBC), so labs can look “normal” even when symptoms are present.

Iron-deficiency anemia occurs later, when iron levels are low enough that your body can no longer make enough healthy red blood cells to carry oxygen. At this point, hemoglobin levels fall.

Not all anemia is caused by iron deficiency. Other causes include vitamin B12 or folate deficiency, chronic inflammation, kidney disease, genetic conditions, or blood loss from sources other than menstruation. This is why identifying the underlying cause of anemia matters before starting treatment.

Many women feel unwell during iron deficiency before anemia develops, which is why hemoglobin alone can miss clinically meaningful iron deficiency.

How Do We Test for Iron Deficiency?

The most useful test for iron deficiency is called ferritin.

Ferritin tells us how much stored iron you have in your body—think of it as your iron “savings account.”

• Low ferritin = low iron reserves
• You can have low ferritin even if other blood tests look “normal”
• Target in iron deficiency is a serum ferritin >100 µg/L unless your health care team has advised otherwise

If your ferritin is low, it doesn’t automatically mean you need a supplement, but it does signal that your body may benefit from extra iron. This leads to the next question: how do you know if you really need an iron supplement?

Before starting iron, it’s important to:

• Confirm iron deficiency with blood work
• Understand why your iron is low

Common reasons iron runs low in women include:

• Heavy or prolonged menstrual periods
• Perimenopause-related cycle changes
• Pregnancy and postpartum recovery
• Low iron intake from food
• Digestive conditions that limit absorption
• Frequent blood donation
• Endurance athletes (BC Guidelines, 2019)

Can Diet Alone Fix Low Iron?

Iron-rich foods are always part of the plan. These include:

• Red meat, poultry, fish
• Beans, lentils, tofu
• Leafy greens
• Iron-fortified grains

Iron from animal sources (heme iron) is absorbed more efficiently than iron from plant-based sources (non-heme iron), which is more sensitive to inhibitors like coffee, tea, and calcium.

However, once iron stores are depleted, food alone often isn’t enough to rebuild them—especially if symptoms are present. That’s when supplements can help.

Choosing the Right Iron Supplement

When you look at an iron supplement, you might notice two numbers on the bottle, which can be confusing.

• The first number is the total size of the pill or liquid
• The second number is the amount of actual iron your body can use, called elemental iron

When choosing an iron supplement, elemental iron is what matters. Typical dosing ranges from 25–60 mg of elemental iron once daily or every other day (BC Guidelines, 2019), but your healthcare provider should guide you on the right dosing for your needs.

The key is finding a supplement you can tolerate and take consistently.

Traditional Iron Salts

These are commonly recommended as they are affordable, covered by drug plans, and are widely available.

Ferrous sulfate

• Elemental iron: 60 mg per tablet
• Pros: Very effective, affordable
• Cons: Most likely to cause nausea, vomiting, constipation, or diarrhea

Ferrous fumarate

• Elemental iron: 100 mg per capsule
• Pros: Higher dose per pill
• Cons: Side effects are common at full doses

Ferrous gluconate

• Elemental iron: 35 mg per tablet
• Pros: Gentler on the stomach
• Cons: Lower dose—may require more pills to reach full dose

Heme Iron Polypeptide

• Elemental iron: 11 mg per tablet

Pros:

• Absorbed more efficiently than non-heme iron
• Gentler on the stomach
• Less affected by food or stomach acid

Cons:

• Derived from animal sources (not vegetarian)
• Low elemental iron content – may require multiple tablets

Polysaccharide or Polydextrose Iron Complex

• Elemental iron: 45–150 mg per capsule / 60 mg per tsp powder

Pros:

• Gentler on the stomach
• Less affected by food
• Available in capsule or powder
• Powder can be mixed into water, juice, or soft foods (good for swallowing difficulties)

Cons:

• Taste may be unpleasant for powders
• Powders may turn food or beverages brown
• Generally less efficient than salts

Liquid Iron Supplements

• Elemental iron: 30–100 mg elemental iron per tsp (5 mL), depending on product

Pros:

• Adjustable dosing
• Easier to take if you can’t swallow pills
• Usually better tolerated than high-dose pills

Cons:

• Can stain teeth (use a straw, rinse afterwards)
• Taste may be unpleasant

Iron Bisglycinate (Chelated Iron)

• Elemental iron: 20–25 mg elemental iron per capsule (varies by brand)

Pros:

• Gentle on the stomach
• Less likely to cause constipation or nausea
• Well absorbed, even at lower doses
• Good choice for long-term use as typically well tolerated

Cons:

• Often more expensive than traditional iron salts

Tips for Taking Iron Supplements

• Take iron on an empty stomach for best absorption, if possible.
• Vitamin C is commonly suggested to enhance absorption, though evidence of meaningful benefit is mixed.
• Avoid taking iron at the same time as coffee, tea, dairy, calcium, or certain medications like antacids, as these can reduce absorption.
• If your stomach is sensitive, it’s okay to take iron with a small amount of food, or take it every other day — this may delay resolution of symptoms and replenishment of iron stores, but improves tolerance.
• Start with a small dose and gradually increase as tolerated.

How Long Until You Feel Better?

This is one of the most important questions.

• Some symptoms improve as early as 4 weeks
• Full iron replenishment often takes up to 6 months
• Follow-up blood work is important to make sure treatment is working to achieve target

Some people don’t absorb iron well or can’t tolerate supplements. In rare cases, iron given through an IV may be recommended.

Key Takeaways

If you’ve been told your labs are “normal” but you still feel exhausted, iron deficiency may still be part of the picture.

The key is:

• Proper testing
• Proper dietary intake
• The right supplement
• The right dose
• Enough time

If something feels off, trust that signal—and talk to a health care provider who understands women’s health across the lifespan.