Iron: A Pharmacist’s Guide to Deficiency, Supplements & Better Absorption

By Lauren O’Reilly, Pharmacist 

Iron is an essential mineral involved in making haemoglobin, the protein in red blood cells that carries oxygen around the body. When iron levels become too low, you can develop iron deficiency and, if it progresses, iron deficiency anaemia. 

But taking an iron supplement isn't always the answer to feeling tired. Iron is something I would ideally supplement based on your individual needs and, where deficiency is suspected, on the basis of blood test results. Taking unnecessary iron can cause side effects and, in excess, can be harmful. It can also mask another issue. Iron supplements can replace the iron your body is lacking, but they don't address the underlying cause of the deficiency. If your iron is repeatedly low or the reason for the deficiency isn't clear, it's important to investigate why rather than simply taking iron indefinitely, or without speaking to your GP first.  

Iron deficiency can happen before you develop anaemia 

Iron deficiency and iron deficiency anaemia aren't quite the same thing. 

Your body stores iron, with ferritin being a useful marker of those iron stores. Your haemoglobin (Hb) is part of the picture too, because it tells us whether you have enough haemoglobin-containing red blood cells to carry oxygen around the body. 

You can therefore have depleted iron stores before your haemoglobin falls enough to be diagnosed with anaemia, or before you notice any symptoms of having low iron. Ferritin is routinely included alongside a full blood count when investigating anaemia, although results need to be interpreted in context because inflammation and some other conditions can affect ferritin levels. 

This is why I wouldn't recommend simply taking iron because you feel tired. If you're concerned about your iron status, speak to your GP about whether blood tests are appropriate. 

What does iron deficiency feel like? 

Iron deficiency anaemia can cause: 

Not everyone will experience the same symptoms, and tiredness alone has many possible causes. Persistent or significant symptoms are worth investigating rather than assuming they are due to low iron, as we must also rule out other possible causes. 

Heavy periods, pregnancy, a diet low in iron and blood loss are among the reasons someone may become iron deficient. Unexplained iron deficiency can sometimes require further investigation to identify the cause. 

So, when might you actually need an iron supplement? 

There isn't one iron supplement that everyone should take. 

If blood tests confirm iron deficiency, the appropriate dose and formulation depend on how low your levels are, why you're deficient, how well you tolerate iron and whether your GP has prescribed a particular treatment. 

Some people may simply need to improve dietary iron intake, while others require supplementation. If you have been prescribed iron for iron deficiency anaemia, follow the treatment and dosing advice given by your GP or pharmacist. 

Good dietary sources include red meat, beans and pulses, nuts, dried fruit and iron-fortified cereals. 

Iron supplements I might consider 

How To Choose The Right Iron

The amount of iron isn't the only thing to consider. Form, dose and tolerability all matter. 

For example, some people find conventional iron salts difficult to tolerate because of gastrointestinal side effects. Active Iron uses a whey-protein-based formulation around ferrous sulphate and is specifically designed to be gentler on the stomach. 

Constipation is one of the most common complaints I hear about with iron supplements. High doses of oral iron can cause gastrointestinal side effects including constipation, nausea and stomach pain. 

This doesn't mean you have to put up with significant side effects. Different iron formulations and doses can be better tolerated by different people, so if your iron is upsetting your stomach, speak to your pharmacist or GP rather than simply stopping treatment. 

How to Take Iron  

Iron is generally absorbed best when taken away from food, although this isn't always practical if it causes stomach upset. 

For conventional ferrous sulphate, the HSE advises taking it on an empty stomach where possible - around 30 minutes before food or 2 hours afterwards. If it causes stomach problems, taking it with or after food may improve tolerance. 

Vitamin C can enhance the absorption of non-haem iron, which is why taking iron with a source of vitamin C, such as orange juice, is sometimes recommended. However, you don't necessarily need a separate high-dose vitamin C supplement if your diet already provides enough. 

Some foods, drinks and supplements can reduce iron absorption. 

I would generally avoid taking your iron alongside: 

Tea and coffee contain compounds that can reduce iron absorption, while calcium can also interfere with absorption. For prescribed iron preparations such as ferrous sulphate, the HSE recommends leaving around a 2-hour gap from tea, coffee and dairy products. 

This doesn't mean you need to avoid these foods altogether - it's mainly about timing them away from your iron supplement. 

How Long Iron Takes to Work… 

This depends on how deficient you are, the cause of the deficiency and the treatment you're taking. 

Some people notice improvements in symptoms within a few weeks, but rebuilding iron stores takes longer. When iron deficiency anaemia is being treated, iron tablets may need to be continued for several months, even after you start feeling better. Repeat blood tests can be used to check whether your levels have recovered. 

So don't assume that feeling better means your iron stores are fully replenished.