An iron supplement
Ferrous gluconate
An oral iron supplement for iron-deficiency anaemia, sometimes better tolerated than other iron salts.
What is Ferrous gluconate?
Ferrous gluconate is an iron supplement used to treat and prevent iron-deficiency anaemia, when the body lacks the iron to make healthy red blood cells. It is one of three common iron salts (with ferrous sulfate and ferrous fumarate); it contains less iron per tablet, which some people find gentler on the stomach. It can still cause harmless black stools, constipation and nausea, eased by taking it with food or on alternate days. Keep it well away from children, because iron overdose can be very dangerous.
Education and reference only. This is a plain-language guide to Ferrous gluconate — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Ferrous gluconate is an oral iron salt used to treat and prevent iron-deficiency anaemia. Iron is needed to make haemoglobin, the oxygen-carrying part of red blood cells, so a shortage causes tiredness, breathlessness and paleness. It contains less elemental iron than ferrous sulfate or fumarate per tablet, which is why some people find it a little gentler. It is taken as a tablet, usually over several months.
How it works
Ferrous gluconate provides iron the gut can absorb, which the body uses to rebuild haemoglobin and healthy red blood cells, easing anaemia over weeks. Because it carries less elemental iron per tablet, some people experience milder stomach effects, though the overall approach is the same as other iron salts. As with all of them, absorption depends on what it is taken alongside.
Company & origin
Originated / developed by: Generic (long-established).
An oral iron salt used in the UK to treat and prevent iron-deficiency anaemia, often chosen for gentler tolerability.
Practical use
How to take Ferrous gluconate
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it with or after food if it upsets your stomach, even though it is absorbed slightly better on an empty stomach.
- Your prescriber may suggest alternate-day dosing if daily iron is hard to tolerate, which can be just as effective.
- Keep it a couple of hours apart from tea, coffee, milk, calcium supplements and antacids, which reduce absorption.
- Vitamin C, such as orange juice, can help your body absorb the iron.
- Keep all iron supplements well out of the sight and reach of children, as an overdose can be very dangerous.
Weighing it up
Advantages & disadvantages of Ferrous gluconate
Advantages
- Often a little gentler on the stomach than higher-iron salts, as it contains less elemental iron.
- An effective and inexpensive option for treating and preventing iron-deficiency anaemia.
- Can be taken on alternate days to reduce side effects.
Disadvantages
- Still commonly causes constipation, nausea and dark stools.
- Contains less iron per tablet, so more tablets may be needed than with other salts.
- Absorption is reduced by food, drinks and several medicines, so timing matters.
Practical use
Good to know
Like all oral iron, it darkens the stools, which is harmless, though black tarry stools with stomach pain should be checked. Constipation, nausea and stomach upset can still occur, and taking it with food or on alternate days helps tolerability. Tea, coffee, milk and calcium reduce iron absorption and are best separated from it, while vitamin C can improve absorption. Iron must be kept out of reach of children because overdose can be very dangerous. Treatment is usually continued for a while after blood counts recover, to rebuild stores.
Who should not take it / use with caution
- People with iron-overload conditions such as haemochromatosis should not take iron unless advised.
- Generally avoided in people who have repeated blood transfusions unless a doctor recommends it.
- Used cautiously in active inflammatory bowel disease or known oral-iron intolerance.
Monitoring
- Blood tests to confirm haemoglobin and iron stores are improving.
- Reviewing tolerability and whether timing or alternate-day dosing helps.
- Looking for an underlying cause of iron deficiency if it persists or returns.
Side effects
- Constipation, nausea, stomach cramps and dark stools are common and usually harmless.
- Diarrhoea or heartburn in some people, often easing with food or alternate-day dosing.
- Rarely, severe stomach pain or black tarry stools that should be checked promptly.
Key interactions
- Reduces absorption of levothyroxine and antibiotics such as tetracyclines and quinolones, so separate the doses.
- Calcium supplements, antacids and tea bind iron and lower how much is absorbed.
- Vitamin C can increase iron absorption; iron can affect certain bisphosphonate and Parkinson's medicines.
Available as: Tablets taken by mouth.
Answers
Ferrous gluconate: frequently asked questions
Why might I be given ferrous gluconate instead of sulfate?
It contains less elemental iron per tablet, which some people find gentler on the stomach, so it may be tried if other iron salts are hard to tolerate.
Does it still turn stools black?
Yes, all oral iron darkens the stools and this is harmless, though black tarry stools with stomach pain should be checked.
Can I take it with calcium tablets?
It is best separated by a couple of hours, as calcium reduces how much iron your body absorbs.
Will it help my tiredness quickly?
Iron-deficiency symptoms such as tiredness usually improve over weeks as your blood count and iron stores recover.
Is it safe around children?
Iron overdose can be very dangerous in children, so keep all supplements well out of their reach.
The wider class
About Iron supplements
Ferrous gluconate belongs to the iron supplements class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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