Ferrous sulfate

What is ferrous sulfate?

Ferrous sulfate is a type of iron supplement that’s widely used to treat or prevent iron deficiency anaemia. It is available on prescription and can also be purchased over the counter. Iron is essential for producing haemoglobin – the protein in red blood cells that carries oxygen around the body – and too little iron in the body can lead to anaemia[1]. 

What is ferrous sulfate used for?

Ferrous sulfate is primarily used to treat iron deficiency anaemia, a condition where the body does not have enough healthy red blood cells due to low iron levels. It can also help prevent anaemia in people at higher risk, such as those who are pregnant or recovering from blood loss[1]. 

How does ferrous sulfate work?

Ferrous sulfate helps replenish the body’s iron stores. Once absorbed, the iron is used to make more red blood cells and haemoglobin, which improves the transport of oxygen throughout the body. This can help reduce symptoms such as tiredness, weakness and shortness of breath[1]. 

Who can take ferrous sulfate?

Ferrous sulfate is usually suitable for most adults and children over the age of 12. However, it may not be suitable for people who have one of the following conditions - a condition affecting iron levels such as haemochromatosis, a condition affecting the red blood cells such as sickle cell disease, certain stomach or bowel problems, have anaemia not caused by iron-deficiency, are having repeated blood transfusions or have noticed blood in your pee[1]. 

Please tell your doctor or pharmacist about any conditions you may have before you start treatment and always follow the instructions in the Patient Information Leaflet[2]. 

How do you take ferrous sulfate?

You should take ferrous sulfate on an empty stomach for best absorption – ideally doing so 30 minutes before or two hours after meals. If you find that the tablet upsets your stomach it can be taken after food but this may decrease the absorption of the iron. Taking it with a drink containing vitamin C, such as orange juice, can help improve absorption. You should avoid taking it with tea, coffee, dairy products or antacids, as these can interfere with how well the iron is absorbed. Swallow the tablets whole, with plenty of fluid - chewing or keeping the tablets in the mouth can cause staining and mouth ulcers[1]. 

What is the typical dosage of ferrous sulfate?

The typical dose for adults is one 200mg tablet taken once, twice or three times daily, depending on the severity of the iron deficiency. The dose for children can vary depending on age, weight and blood results, and it should only be given under medical supervision[1]. 

Can you stop taking ferrous sulfate suddenly?

If you’re taking ferrous sulfate, you shouldn’t stop taking it without first consulting a doctor. Even if your symptoms have improved, treatment can continue for several months to make sure that the body’s iron stores are fully restored[1]. 

What should you do if you take too much ferrous sulfate?

Taking too much ferrous sulfate can be harmful, especially for children. Iron tablets should be kept out of sight and reach of children as an overdose can be fatal. The most common symptoms of a ferrous sulfate overdose are nausea and vomiting, stomach pain, diarrhoea, and dizziness. If you suspect that you or someone else have taken an overdose, seek immediate medical attention, even if symptoms do not seem severe[1]. 

What should you do if you forget a dose of ferrous sulfate?

If you forget to take a dose of ferrous sulfate, you can take it as soon as you remember. However, if your next dose is due soon, skip the missed dose and take the next one as normal. You should never take two doses at the same time[1]. 

What medicines should you avoid while taking ferrous sulfate?

Ferrous sulfate can interact with certain other medicines. This can reduce their effectiveness or increase the risk of side effects. it is generally recommended to leave a gap between taking ferrous sulfate and any other medicines. In particular, ferrous sulfate can interact with[1]:  

• Antacids and proton pump inhibitors, such as omeprazole 

• Some antibiotics, including tetracyclines and ciprofloxacin 

• Thyroid medicines such as levothyroxine 

• Antivirals used for HIV such as dolutegravir 

• Laxatives containing magnesium 

• Bisphophonates used for osteoporosis, such as alendronate 

• Medication for parkinsons such as levodopa, carbidopa or entacapone 

• Supplements containing iron, calcium, magnesium or zinc 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

What are the side effects of ferrous sulfate?

The most common side effects of ferrous sulfate are experiencing stomach discomfort, nausea, constipation, diarrhoea, and black staining on the teeth. You can take the medication with food if you are experiencing nausea or heartburn, increase fluid and fibre intake for constipation and diarrhoea, rinse the mouth out after taking the drops and do not keep the tablets in the mouth to help with staining on the teeth. You may also notice having darker-coloured stools – this is usually harmless and expected when taking ferrous sulfate[1]. 

If you experience side effects that are severe or do not improve, speak to your doctor. They may adjust your dosage or suggest a different form of iron. If you notice black, tar like stools or blood in your stool and you feel unwell in any way, seek medical attention straight away[1]. 

You should contact your GP if you experience any of these symptoms. In rare cases, the medicine may cause a serious allergic reaction (anaphylaxis). You should call 999 or visit A&E immediately if you believe this is happening[1]. 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2]. 

Frequently asked questions about ferrous sulfate

How long does it take for ferrous sulfate to work? 

You may start to feel better after 3-4 weeks of taking ferrous sulfate. However, it usually takes between three and six months to fully treat iron deficiency anaemia, so you should continue taking your treatment as prescribed, even if your symptoms improve quickly. If you are taking the medication to prevent anaemia, you will continue to take it as long as you are at risk of anaemia, your doctor can advise more on this[1]. 

Can I take ferrous sulfate during pregnancy? 

Ferrous sulfate is often prescribed during pregnancy to prevent or treat anaemia. It is also safe to use when breastfeeding. If you baby has low iron levels they will need separate treatment, as not enough passes into the breast milk to treat iron-deficiency. You should only take it under the guidance of your healthcare provider[1]. 

Can I drink alcohol while taking ferrous sulfate? 

You can usually drink alcohol safely while taking ferrous sulfate, however, excessive amounts may worsen anaemia and irritate your stomach[1]. 

Is ferrous sulfate suitable for vegetarians or vegans? 

Ferrous sulfate itself is normally suitable for vegetarians and vegans. Some tablet coatings, though, may contain animal-derived ingredients. If you follow a vegetarian or vegan diet, ask your pharmacist to confirm whether a specific product is suitable[1]. 

Can lifestyle changes help with iron-deficiency?  

Some iron-deficiencies may be caused by a lack of iron in the diet. In these cases it may help to include more sources of iron in the diet such as: dark green leafy vegetables, beans, lentils, nuts, dried fruits, wholegrains and fortified cereals[1]. 

For the official NHS guide to ferrous sulfate, visit their website.