Ferrous sulfate (or sulphate) is a medicine used to treat and prevent iron deficiency anaemia.

Iron helps the body to make healthy red blood cells, which carry oxygen around the body. Some things such as blood loss, pregnancy or too little iron in your diet can make your iron supply drop too low, leading to anaemia.

Ferrous sulfate comes as tablets, or as drops that you swallow.

There are modified-release tablets and capsules of ferrous sulfate, but they may not be absorbed as well.

It's available on prescription and to buy from pharmacies.

Ferrous sulfate may also be called by the brand names Feospan, Ferrograd, and Ironorm Drops.

• Ferrous sulfate works best when taken on an empty stomach. However if it gives you stomach ache, try taking it with food.
• Most people begin to feel better after taking ferrous sulfate for 1 week, but it may take up to 4 weeks to take full effect.
• Common side effects include feeling or being sick, constipation and diarrhoea.

Most adults and some children aged 12 years and over can take ferrous sulfate under the advice of a doctor or pharmacist.

Ferrous sulfate may not be suitable for everyone.

To make sure it's safe for you, tell your doctor before taking ferrous sulfate if you:

• have had an allergic reaction to ferrous sulfate or any other medicine in the past
• have a different type of anaemia that is not caused by low levels of iron
• have any other conditions that affect your iron levels, such as haemochromatosis or haemosiderosis
• have a condition that affects your red blood cells, such as sickle cell anaemia or thalassaemia
• have a stomach ulcer, have had all or part of your stomach removed, or have other stomach or bowel problems such as inflammatory bowel disease
• are receiving repeated blood transfusions
• have noticed blood in your pee
• have been diagnosed with an iron deficiency and are already receiving treatment for this

If you or your child are prescribed ferrous sulfate, follow a doctor's instructions about how and when to take it.

If you buy ferrous sulfate from a pharmacy, follow the instructions that come with the packet.

Ferrous sulfate comes as 200mg tablets or as drops that you swallow.

The drops contain 125mg of ferrous sulfate in each 1ml.

The drops may be easier for children and people who find it difficult to swallow tablets.

How much will I take?

The dose of ferrous sulfate depends on why you're taking it and whether you have tablets, capsules or drops.

For children under the age of 18 years, the doctor will use your child's age, weight and blood results to work out the right dose.

To treat anaemia

The usual dose for adults is:

• tablets: one 200mg tablet, taken 2 to 3 times a day
• drops: 4ml, taken once or twice a day

To prevent anaemia

The usual dose for adults is:

• tablets: one 200mg tablet, taken once a day
• drops: 2.4ml to 4.8ml daily

How to take it

Ferrous sulfate works best when you take it on an empty stomach. However, if it upsets your stomach, you can take it with or after food.

A doctor (or a pharmacist) may recommend taking ferrous sulfate with orange juice or a vitamin C supplement. Vitamin C is believed to increase the amount of iron absorbed by the body.

Swallow the tablet or capsule whole with a glass of water. Do not suck, chew or keep the tablet in your mouth as this can cause mouth ulcers or stain your teeth.

Do not take it with tea, coffee, eggs, dairy products and soybean products, as they can reduce the amount of iron that gets into your system. When you take ferrous sulfate (or when you eat foods that are high in iron), leave a 2-hour gap before having these foods or drinks.

If you have difficulty swallowing the tablets tell your doctor or pharmacist.

If you're taking ferrous sulfate as drops, it will come with a plastic syringe or dropper to help you measure out the right dose.

If you do not have one, ask a pharmacist for one. Do not use a kitchen teaspoon as it will not give you the right amount of medicine.

What if I forget to take it?

If you forget a dose, take another as soon as you remember. If it's almost time to take the next dose, then do not take the missed dose at all.

Do not take a double dose to make up for a forgotten dose.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to remember your medicine.

What if I take too much?

If you go to A&E do not drive yourself. Get someone else to drive you, or call an ambulance.

Take the ferrous sulfate packet or the leaflet inside it with you and any remaining medicine.

Like all medicine, ferrous sulfate can cause side effects in some people.

Many people have no side effects or only minor ones.

Talk to a pharmacist or doctor if these side effects bother you or do not go away:

• feeling or being sick (nausea or vomiting), stomach pain or heartburn
• loss of appetite
• constipation
• diarrhoea
• dark or black poo
• black stained teeth (from the drops)

Serious allergic reaction

In rare cases it's possible to have a serious allergic reaction (anaphylaxis) to ferrous sulfate.

These are not all the side effects of ferrous sulfate.

For a full list, see the leaflet inside your medicines packet.

What to do about:

• feeling or being sick, stomach pain or heartburn – try taking ferrous sulfate with, or just after, a meal or snack. Stick to simple meals and do not eat rich or spicy food. If you're being sick, try small frequent sips of water to avoid dehydration. Signs of dehydration include peeing less than usual or having dark strong-smelling pee.
• loss of appetite – eat when you would usually expect to be hungry. If it helps, eat smaller meals more often than usual. Snack when you're hungry. Have nutritious snacks that are high in calories and protein, such as dried fruit and nuts.
• constipation – eat more high-fibre foods such as fresh fruit, vegetables and cereals, and drink plenty of water. Try to exercise more regularly, for example, by going for a daily walk or run. If this does not help, talk to a pharmacist or doctor. Watch this short video about how to treat constipation.
• diarrhoea – drink lots of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
• dark or black poo – this is common when taking iron and is nothing to worry about. Talk to a doctor if your poo is black and sticky looking, has red streaks in it, or if you also feel unwell in any other way.
• black stained teeth – rinse your mouth with water after taking the drops. Do not suck or chew the tablet, or keep it in your mouth.

It's usually safe to take ferrous sulfate during pregnancy.

Speak to a doctor, who'll be able to explain the benefits and the risks of taking ferrous sulfate when pregnant. They can help you decide on the best treatment for you and your baby.

If you are pregnant and taking iron supplements, you can often become constipated or develop piles (haemorrhoids). If this happens to you, talk to a doctor. They can advise you on the best way to deal with constipation or haemorrhoids.

Ferrous sulfate and breastfeeding

It's usually safe to breastfeed while taking ferrous sulfate.

However, some of the medicine may pass into your breast milk. This is in small amounts and is unlikely to harm your baby.

Talk to a doctor if you want to breastfeed while taking ferrous sulfate. They can advise you on what's best for you and your baby.

There are some medicines that may interfere with how ferrous sulfate works. Ferrous sulfate can also affect the way other medicines work.

It is a good idea to leave a gap between taking the other medicine and ferrous sulfate. Some medicines should not be taken for 2 hours before or after taking ferrous sulfate. Ask a doctor or pharmacist for advice on how long the gap should be.

Tell a pharmacist or doctor if you're taking these medicines before you start taking ferrous sulfate:

• supplements or multivitamins containing iron, calcium, magnesium or zinc, or you are already receiving iron injections
• antacids or indigestion remedies
• antibiotics such as oxytetracycline, doxycycline, ciprofloxacin or chloramphenicol
• antivirals used for HIV infection such as bictegravir or dolutegravir
• laxatives containing magnesium such as magnesium hydroxide and Milk of Magnesia
• bisphosphonates such as alendronic acid and risedronate (medicines used to treat or prevent osteoporosis)
• cholestyramine, a medicine used to reduce cholesterol and treat itching caused by liver disease
• eltrombopag, a medicine used to increase platelets in the blood
• levothyroxine, a medicine used to treat an underactive thyroid
• levodopa, carbidopa or entacapone, medicines used to treat Parkinson’s disease
• mycophenolate, a medicine used after an organ transplant
• methyldopa, a medicine used to treat high blood pressure
• penicillamine, a medicine used to treat arthritis
• trientine, a medicine used to treat Wilson's disease

Mixing ferrous sulfate with herbal remedies or supplements

Talk to a pharmacist or doctor before taking any herbal remedies or supplements together with ferrous sulfate. Some vitamin and mineral supplements may already contain ferrous sulfate or other types of iron.

Tell the pharmacist or doctor if you take any supplements or remedies that contain iron, calcium, magnesium or zinc. Ferrous sulfate can stop zinc working as well as it should.