Ferrous sulfate
Ferrous sulfate is an iron salt used to treat or prevent iron-deficiency anaemia when your GP has confirmed low iron or a clear need (for example after blood loss or in pregnancy under supervision). It is not a general tonic — unnecessary iron can cause harm.
This medicine is part of the Blood pressure, cholesterol & related category.
Generic name: ferrous sulfate
Quick answers
Short replies to searches people often run before speaking to a clinician. For the overview of what the medicine is used for, see the short summary under the page title above.
What is it for?
Ferrous sulfate is an iron salt used to treat or prevent iron-deficiency anaemia when your GP has confirmed low iron or a clear need (for example after blood loss or in pregnancy under supervision).
How long does it take to work?
Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review.
What are common side effects?
Very common effects include constipation, dark or black stools (harmless colour change), nausea, abdominal pain, and wind.
Can you take paracetamol or ibuprofen with it?
Ask your GP or pharmacist before taking Ferrous sulfate with paracetamol or ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
More about what Ferrous sulfate is used for
Ferrous sulfate is an iron salt used to treat or prevent iron-deficiency anaemia when your GP has confirmed low iron or a clear need (for example after blood loss or in pregnancy under supervision).
It is not a general tonic — unnecessary iron can cause harm.
How does Ferrous sulfate work, and how long does it take to work?
Iron is a building block of haemoglobin in red blood cells. Replacing iron allows the bone marrow to make healthier red blood cells over weeks.
Haemoglobin and ferritin blood tests help judge response.
How and when should you take Ferrous sulfate?
Usually taken once or twice daily on an empty stomach if tolerated, or with food if it upsets your stomach — follow your prescriber or pharmacist, as absorption differs.
Vitamin C (for example orange juice) with tablets can improve absorption for some formulations. Leave a gap between iron and antacids, thyroxine, and some antibiotics — your pharmacist can advise spacing.
What are the common side effects of Ferrous sulfate?
Very common effects include constipation, dark or black stools (harmless colour change), nausea, abdominal pain, and wind.
Liquid forms may stain teeth — use a straw and brush teeth after if advised.
Serious side effects of Ferrous sulfate — when to get urgent help
Iron overdose is dangerous, especially for children — keep all medicines out of reach. Seek emergency help if a child swallows iron tablets.
Severe vomiting, diarrhoea, or allergic reaction need urgent advice.
What if you miss a dose of Ferrous sulfate?
If you miss a dose, take it when you remember unless nearly time for the next. Do not double up.
Who should not take Ferrous sulfate?
Do not take for anaemia until type is known — B12 or folate deficiency, thalassaemia, or haemochromatosis need different treatment.
Some people with inflammatory bowel flare-ups or repeated transfusions must not take iron without specialist advice.
Can you take paracetamol or ibuprofen with Ferrous sulfate? — other interactions
Levothyroxine, bisphosphonates, quinolone and tetracycline antibiotics, and PPIs can reduce iron absorption if taken together — spacing doses helps.
Tea and coffee around tablet time may reduce absorption.
Ferrous sulfate in pregnancy and breastfeeding
Iron is often used in pregnancy when deficient; dose and monitoring are guided by your midwife or GP.
Blood tests and monitoring on Ferrous sulfate
Blood tests (haemoglobin, ferritin) are repeated to confirm improvement and decide how long to continue.
What might your GP prescribe instead of Ferrous sulfate?
Other iron salts (ferrous fumarate, ferrous gluconate), liquid iron, or intravenous iron in hospital may be used if tablets are not tolerated or absorption is poor.
Reviewed by UK registered pharmacists
Reviewed by UK registered pharmacists for accuracy and clarity. Content is informational only.
- Professional registration
- GPhC registration number: [placeholder — to be added when verified]
- Last reviewed
Frequently asked questions about Ferrous sulfate
People also ask — common Google searches
- What is Ferrous sulfate used for?
- Ferrous sulfate is an iron salt used to treat or prevent iron-deficiency anaemia when your GP has confirmed low iron or a clear need (for example after blood loss or in pregnancy under supervision). It is not a general tonic — unnecessary iron can cause harm.
- How long does Ferrous sulfate take to work?
- Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review. Always follow your prescriber’s follow-up plan.
- Can you take Ferrous sulfate with paracetamol or ibuprofen?
- Ask your GP or pharmacist before taking Ferrous sulfate with Paracetamol or Ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
- What are the side effects of Ferrous sulfate?
- Very common effects include constipation, dark or black stools (harmless colour change), nausea, abdominal pain, and wind. Liquid forms may stain teeth — use a straw and brush teeth after if advised. See the sections below for more detail, including serious side effects and when to seek urgent help.
- Why are my stools black on iron?
- Unabsorbed iron darkens the stool. This is common. If you also have severe tummy pain, vomiting blood, or black tarry stools with other symptoms, seek medical advice to rule out bleeding.
- How long until iron tablets work?
- Energy may improve over 2–4 weeks; haemoglobin can take longer to rise fully. Continue as directed until your GP confirms you can stop.
Need personalised advice?
Your local pharmacist or GP surgery can help with questions about your medicines, side effects, and alternatives that may be suitable for you.
Links open the NHS website for finding services. DrugABC does not sell prescription-only medicines or replace clinical care.
Often used with
People searching for Ferrous sulfate often read about these medicines too — for example when treatments are combined under GP or specialist care. This is not a prescribing suggestion.
Related medicines
You may also find these informational pages helpful. Each link opens a full guide on DrugABC. Your prescriber decides what is appropriate for you.