Understanding What are the risks of Maltofer?

October 6, 2025 •

4 min read

Maltofer (iron polymaltose) is an oral iron supplement clinically shown to correct iron levels with significantly fewer gastrointestinal side effects compared to traditional ferrous iron supplements. However, like any medication, it is vital for patients to be aware of what are the risks of Maltofer before beginning treatment.

Quick Summary

This article details the safety profile of Maltofer, an iron supplement containing iron polymaltose. It covers the incidence of common gastrointestinal side effects, the potential for rare but serious allergic reactions, important contraindications, and the low risk of overdose associated with the medication.

Key Points

Less Constipation and Nausea: Compared to ferrous sulfate, Maltofer is significantly less likely to cause common gastrointestinal side effects like constipation and nausea due to its controlled iron absorption mechanism.
Allergic Reaction Risk: A risk of hypersensitivity (allergic reaction) to iron polymaltose exists, with symptoms including skin rash, itching, hives, and swelling of the face, lips, or tongue.
Contraindications are Crucial: Maltofer is not for everyone; it is contraindicated for patients with iron overload disorders (hemochromatosis) or anemia not caused by iron deficiency.
Overdose is Low Risk: Due to its controlled absorption, the risk of acute, severe iron toxicity from a single Maltofer overdose is low, but chronic misuse can still lead to iron overload.
Monitoring is Key for Safety: Regular blood monitoring by a doctor is essential during therapy to track iron levels and prevent potential issues from chronic accumulation.
Syrup Formulation Considerations: The liquid form contains sorbitol and certain preservatives, which can cause allergic reactions or a laxative effect in sensitive individuals.
Fewer Drug Interactions: Maltofer has fewer interactions than ferrous salts; notably, it can be taken with food, and its absorption is not significantly inhibited by common foods like tea or coffee.

Maltofer: A Therapeutic Iron Option

Maltofer is a brand name for a therapeutic oral iron supplement with the active ingredient iron polymaltose. Unlike traditional iron supplements that use ferrous salts, Maltofer features a different chemical structure. This controlled absorption mechanism is a key reason why it is often better tolerated, resulting in significantly fewer gastrointestinal side effects for many patients. It is frequently recommended for individuals who experience intolerance to conventional ferrous iron supplements. While the tolerability is a major advantage, it does not mean the medication is free from risks.

Common Gastrointestinal Side Effects

The most widely recognized and anticipated side effect of Maltofer is the darkening or blackening of stools, which is considered a very common and clinically harmless outcome of oral iron supplementation. While generally less severe than those caused by ferrous salts, other gastrointestinal issues can occur. Clinical trial data compiled in a meta-analysis of 24 studies on Maltofer showed the following commonly reported side effects:

Nausea
Constipation
Diarrhea
Abdominal pain or discomfort
Bloating
Indigestion

Allergic Reactions and Less Common Risks

While rare, some individuals may experience a hypersensitivity or allergic reaction to Maltofer or one of its inactive ingredients. In the case of the syrup or drops, preservatives like methyl and propyl hydroxybenzoate may trigger such a reaction. Symptoms of an allergic reaction can include:

Skin rashes, itching, or hives
Swelling of the face, lips, tongue, or throat
Shortness of breath, wheezing, or difficulty breathing

Less serious but still uncommon side effects can also manifest, such as headaches, muscle spasms, or temporary tooth discoloration with the liquid form. Any severe or persistent symptoms warrant immediate medical attention.

Contraindications: Who Should Not Take Maltofer?

Maltofer is not suitable for everyone, and it is crucial to consult a healthcare professional to confirm its appropriateness. The use of Maltofer is contraindicated in several conditions:

Known Hypersensitivity: Individuals with a previous allergic reaction to iron polymaltose or any other ingredients in Maltofer should not use it.
Iron Overload: Patients with conditions causing excess iron accumulation, such as hemochromatosis or hemosiderosis, should avoid Maltofer.
Non-Iron-Deficiency Anemia: The medication is ineffective for and should not be used to treat anemia not caused by iron deficiency (e.g., hemolytic anemia or vitamin B12 deficiency).
Children Under 12: Maltofer is not recommended for pediatric use in children under 12 years of age.
Hereditary Intolerances: The syrup and drops contain excipients like sorbitol and sucrose. Patients with rare hereditary problems such as fructose intolerance or glucose-galactose malabsorption should not take these formulations.

Comparison of Maltofer and Ferrous Sulfate Side Effects

The decision to use Maltofer is often based on its improved tolerability profile compared to ferrous sulfate, a common alternative. The table below summarizes the key differences in reported side effects based on clinical evidence:


Side Effect	Maltofer (Iron Polymaltose)	Ferrous Sulfate	Reason for Difference
Constipation	Significantly lower incidence	Higher incidence	Maltofer's controlled absorption releases less free iron into the gastrointestinal tract.
Nausea & Vomiting	Fewer occurrences, generally milder	More frequent	The controlled, active absorption reduces direct irritation of the stomach lining.
Abdominal Pain	Less frequent	More common	Less free iron and lower irritation lead to a milder gastrointestinal profile.
Absorption with Food	Can be taken with food, which may enhance absorption	Should be taken on an empty stomach; absorption can be inhibited by food and drink.

Overdose and Chronic Use Risks

Due to the low toxicity of iron polymaltose and its regulated uptake by the body, an accidental fatal overdose is considered highly unlikely with Maltofer. However, taking more than the recommended dose can still cause unpleasant symptoms like headache, nausea, vomiting, or diarrhea. A more significant risk is associated with chronic, unmonitored use. If Maltofer is taken over a long period by someone who is not iron-deficient (e.g., a patient with misdiagnosed anemia), it can lead to iron overload, which may cause liver damage or other organ complications. This highlights the importance of using Maltofer only after a confirmed diagnosis and under medical supervision.

Drug Interactions

In contrast to ferrous salts, Maltofer has fewer known drug interactions. Its absorption is not significantly affected by common food and drink, nor does it typically interfere with the absorption of certain antibiotics in the same way ferrous salts do. The most critical interaction to be aware of is with injectable iron medicines. If a patient is undergoing injectable iron therapy, oral iron like Maltofer should not be taken concurrently.

The Importance of Monitoring and Professional Guidance

Throughout Maltofer therapy, it is important to have iron levels and other relevant blood markers (like serum ferritin) monitored regularly by a doctor. This ensures that the treatment is working effectively and that the risk of iron overload is minimized. While Maltofer is considered a safer alternative for many, especially regarding gastrointestinal side effects, it is not without risk. For comprehensive information and personalized medical advice, patients should consult their healthcare provider, especially if they are pregnant or breastfeeding. Additional information can also be found in product leaflets or on the official website of the manufacturer or distributor, such as the Consumer Medicine Information on the Medsafe website.

Conclusion

Maltofer offers a valuable therapeutic option for treating iron deficiency, particularly for those who cannot tolerate the harsher gastrointestinal side effects of ferrous salt supplements. Its active ingredient, iron polymaltose, provides a more controlled absorption, which contributes to its improved tolerability. However, patients must be fully aware of what are the risks of Maltofer, which include potential but uncommon allergic reactions, important contraindications for individuals with iron overload or non-iron-deficiency anemia, and the need for regular monitoring to prevent chronic issues. By following a doctor's guidance and understanding the associated risks, patients can safely and effectively manage their iron deficiency.

Frequently Asked Questions

Maltofer is generally considered safer and better tolerated regarding gastrointestinal side effects, such as constipation and nausea, compared to conventional ferrous salt supplements (e.g., ferrous sulfate). However, it is not risk-free and carries its own set of potential side effects and contraindications.

The most common and expected side effect is a dark or black discoloration of the stools, which is harmless. Other common side effects include nausea, abdominal pain, diarrhea, constipation, and bloating.

Yes, some people may experience a hypersensitivity or allergic reaction to iron polymaltose or other ingredients in Maltofer. Symptoms can include a skin rash, itching, hives, or swelling of the face, lips, or tongue. If these occur, seek immediate medical attention.

Maltofer is contraindicated for individuals with iron overload conditions (hemochromatosis), anemia not caused by iron deficiency, disturbances in iron utilization, or a known allergy to its ingredients. It is also not for children under 12.

Maltofer is considered suitable for use during pregnancy and is often chosen due to its better tolerability. However, as a precautionary measure, you should always consult your doctor before starting any medication while pregnant or breastfeeding.

While the risk of severe acute iron poisoning is low due to Maltofer's controlled absorption, taking an overdose can cause symptoms like headache, nausea, vomiting, and diarrhea. Chronic, unmonitored use can lead to iron overload, which can damage organs over time.

Maltofer has fewer interactions than other iron supplements. It can be taken with food, as its absorption is not significantly affected. The main interaction to avoid is concurrent use with injectable iron medicines. Always inform your doctor or pharmacist about all medications and supplements you are taking.