Iron Bisglycinate vs Iron Sulphate for Perimenopause: Which Is Easier to Take?
Iron deficiency is common during perimenopause, especially with heavy periods. Compare iron bisglycinate and iron sulphate on absorption, side effects, and tolerability.
Iron Deficiency and Perimenopause
Heavy or irregular periods are among the most common experiences of early perimenopause. For many women, this leads to iron deficiency or frank iron deficiency anaemia, bringing symptoms such as exhaustion, breathlessness, brain fog, and poor concentration. These symptoms overlap significantly with other perimenopause complaints, which means iron deficiency is sometimes missed or attributed entirely to hormonal change. A simple blood test measuring ferritin, haemoglobin, and serum iron can identify whether low iron is contributing to how you feel. If it is, supplementation is usually recommended, and the form of iron you take can make a real difference to how well you tolerate it.
Iron Sulphate: The Standard Option
Iron sulphate (also spelled sulfate) is the most commonly prescribed form of iron in the UK. It is inexpensive, widely available, and effective at raising iron levels. Standard doses contain 200mg of iron sulphate, providing around 65mg of elemental iron, which is a relatively high dose. The downside is that iron sulphate is notorious for gastrointestinal side effects. Constipation, nausea, stomach cramping, and dark stools are reported by a large proportion of women taking it. These side effects lead many people to stop taking it before their levels recover, which defeats the purpose of supplementation.
Iron Bisglycinate: A Gentler Alternative
Iron bisglycinate is a chelated form of iron where the iron molecule is bound to two glycine amino acids. This structure makes it more stable in the digestive tract and better absorbed through the intestinal wall via amino acid transport pathways rather than relying solely on standard iron absorption mechanisms. The result is that iron bisglycinate achieves comparable or better uptake at a lower elemental dose, which means less unabsorbed iron sitting in the gut causing irritation. Studies comparing the two forms have found that iron bisglycinate produces significantly fewer gastrointestinal side effects while still raising ferritin levels effectively.
Comparing Tolerability and Effectiveness
The key practical difference is tolerability. For women who cannot take iron sulphate due to constipation or nausea, iron bisglycinate is usually the recommended alternative. It typically contains 14mg to 20mg of elemental iron per tablet, which looks lower on the label but absorbs more completely. Because it causes fewer side effects, women are more likely to take it consistently, which is the most important factor in correcting iron deficiency. In clinical settings, iron bisglycinate is increasingly the first choice rather than a fallback, particularly for women with sensitive digestion or IBS.
Who Each Form Suits
Iron sulphate suits women who tolerate it well and want an inexpensive, reliable, widely available option. It is typically the first prescription choice. Iron bisglycinate suits women who have tried iron sulphate and found the side effects unmanageable, those with IBS or sensitive digestion, or those who prefer a lower-dose supplement they can take consistently. Both forms should ideally be taken with vitamin C or a vitamin C-rich food to enhance absorption. Avoid taking iron within two hours of tea, coffee, dairy products, or calcium supplements, as these reduce absorption significantly.
Practical Steps Forward
If fatigue and brain fog are among your most significant perimenopause symptoms, ask your GP to test ferritin alongside a full blood count, as many anaemia panels only check haemoglobin and can miss early iron depletion. If you have been prescribed iron sulphate and found it too harsh, it is entirely reasonable to ask about bisglycinate alternatives. The goal is a form you will actually take. Consistent supplementation over three to six months is usually what it takes to replenish iron stores. Logging your energy and other symptoms over time can help you and your doctor gauge progress. PeriPlan lets you track daily symptom patterns so you can see whether fatigue and brain fog begin to lift.
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