7 top-rated iron supplements to boost your energy, recommended by a nutritionist (2025)

Iron is an essential nutrient, and yet at least 1 in 5 women of reproductive age and 4 in 10 pregnant people in the UK are iron deficient. Including me.

For most people, eating a balanced diet – one that includes dark leafy greens, legumes, red meat, poultry, eggs, fish, whole grains, nuts, and fruit – is an easy way to make sure you’re getting enough iron. But, during pregnancy, the amount of blood in a woman’s body increases, which means she needs more iron for herself and her growing baby.

I’m currently pregnant – so it’s hardly surprising, given how common anaemia can be in pregnancy, that my latest batch of blood tests (taken during my routine antenatal appointment at 28 weeks) came back showing low iron levels.

Most people with anaemia in pregnancy go on to have a healthy pregnancy and baby. However, if left untreated, iron deficiency anaemia has been linked to pregnancy complications including; low birth weight, premature labour, and a higher risk of needing a blood transfusion in labour.

What causes iron deficiency anaemia? You are more likely to develop iron-deficiency anaemia in pregnancy if you: are vegetarian or vegan, have had anaemia before, are carrying more than one baby, were younger than 20 when you got pregnant, have had 3 or more babies, you’re pregnant again after having a baby within the last year.

The easiest way to treat iron deficiency? With iron supplements, of course.

How long do iron supplements take to work?

Sadly, iron deficiency isn’t something that can just be magically corrected overnight. You may need to take iron supplements regularly for weeks – sometimes longer – to properly replenish your iron reserves.

‘Iron supplements typically take a few weeks to start improving iron levels, but it can take three to six months to fully replenish stores, depending on the severity of the deficiency,’ explains Healf’s Head Nutritionist, Eleanor Hoath.

‘Regular blood tests can help track progress. If levels aren’t improving as expected, gut health and absorption issues may need to be addressed. Supporting gut health alongside iron intake can make a big difference in improving levels.’

If you’re pregnant and your haemoglobin levels do not rise after trying iron supplements, you may be referred to a haematologist and given iron through an intravenous (IV) drip.

RELATED: 6 weird signs you have an iron deficiency

Do iron supplements make you constipated?

The short answer? Yes.

‘Iron supplements can cause constipation, especially the more commonly prescribed ferrous sulfate,’ says Hoath.

‘If constipation occurs, choosing a gentler form such as iron bis-glycinate is advised as well as increasing fibre intake, and supporting gut bacteria with probiotics can help. I also recommend clients include food sources of vitamin C in their routine to optimise the absorption of iron too.’

While constipation when you first take iron supplements is normal, if you are worried call your GP. Any side effects should get better over time. If they don’t, your doctor may advise you to take iron supplements every other day instead, or they may prescribe a lower dose.

What’s better: liquid iron supplements or capsules?

Iron in tablet form is just as well absorbed as iron in a liquid supplement, according to a 2013 study. So, choosing the right one for you usually comes down to personal preference.

‘Liquid iron is often gentler on digestion, making it a good option for those with absorption issues or sensitive stomachs,’ says Hoath.

‘However, capsules can be more convenient and have fewer issues with taste. The best choice depends on individual needs, and in some cases, pairing iron with gut-supporting nutrients can improve overall absorption.’

RELATED: What are iron-rich foods? The best meat, vegetables and pulses to naturally level up

When should you take iron supplements?

Research has shown you will absorb more of the iron in your supplement if you take it on an empty stomach.

‘Iron is best absorbed on an empty stomach, ideally first thing in the morning or between meals,’ says Hoath.

However, taking an iron supplement without food can cause stomach issues and nausea in some people. So if you do take your iron supplement with food, you need to think about which foods will boost (not limit) iron absorption.

‘Taking it with a small amount of food (avoiding dairy, tea, and coffee, which inhibit absorption) can help. Pairing iron with vitamin C (like a squeeze of lemon in water) can significantly enhance absorption,’ adds Hoath.

If you are taking medication or under medical supervision, please consult your GP before taking any food supplement.

7 best iron supplements for 2025, according to a nutritionist

Floradix liquid iron was the first product suggested to me by my midwife. She recommended taking this supplement first thing in the morning, since the body can absorb significantly more iron earlier in the day. As it’s a liquid, it’s arguably easier to take than a giant tablet (or three). Floradix also contains vitamins B2, B6, B12 and C which all contribute to the reduction of tiredness and fatigue, while vitamin C increases iron absorption.

Spatone liquid iron supplement was another recommended by my midwife – since it’s gentle and less likely to cause stomach upset and constipation. You simply add the sachet to water or fruit juice high in vitamin C (to help increase the absorption of iron) – a great alternative to tablets.

Created by founder and nutritionist Jessica Sepel, this Iron+ formula from JS Health aims to reduce feelings of tiredness and fatigue, plus support energy levels. Each tablet contains 24mg of iron, and also includes B vitamins and vitamin C for increased absorption.

Gentle and easily absorbed, this iron supplement from BlueIron is made with Nordic blueberry concentrate for a great taste. Packed with essential vitamins and minerals – including vitamin C, vitamin B12 and folic acid, this iron supplement comes highly recommended for reducing tiredness and supporting overall wellbeing.