When more isn’t better: finding the supplement sweet spot

From vitamin D to iron, we explore the risks of taking too many supplements and how to use supplements safely with a food-first approach

Walk into any pharmacy or scroll online, and you’ll find shelves filled with supplements promising more energy, brighter moods, better immunity, and a more peaceful, natural night’s sleep. With so many marketed as natural, healthy, and holistic, it’s no wonder that, for many of us, taking a supplement feels like a small, simple step towards looking after ourselves and supporting our health. And sometimes, they can be good for us. But sometimes? We might not have enough information about what we're taking, and if we really need it.

Sometimes, supplements are recommended. Current guidelines in the UK advise us that, while most people should be able to get the nutrients they need from a varied, balanced diet, specific supplements, like vitamin D during the autumn and winter months, are recommended. During specific life events, like when someone is pregnant, they may be advised to take certain prenatal vitamins at different stages.

And this is where misunderstanding can creep in. Because while supplements can support health in the right context, taking more than recommended – supplementing without guidance – can carry risks. Taking high doses, particularly over time, can cause side effects or more serious health problems. Understanding what your body needs – and when to seek advice – can help you avoid deficiency without tipping into excess.

Can you take too much vitamin D?

Vitamin D helps us build and keep our bones and muscles healthy. Without enough vitamin D, your body struggles to absorb calcium, a major mineral essential for strong bones and teeth. When we don’t get enough vitamin D, it can lead to overall fatigue and muscle weakness or aching, bone pain, and low mood, and can weaken your immune system. 

In the UK, we get most of the vitamin D we need from direct sunlight on our skin when we are outdoors, but in the autumn and winter months, we don’t make enough vitamin D from sunlight alone. During autumn and winter – and for people who spend little time outdoors, cover most of their skin, or have darker skin tones – sunlight alone may not be enough.

Vitamin D is found naturally in only a small number of foods, including oily fish, egg yolks and fortified products. Current guidelines in the UK suggest taking vitamin D supplements between October and March.

While vitamin D is essential, it is possible to take too much. Taking high doses over a long period can cause too much calcium to build up in the body (hypercalcaemia), which may lead to nausea, weakness, kidney problems and, in severe cases, heart complications. Sticking to NHS guidance and seeking advice if unsure can help ensure you’re supporting your health safely.

How much is too much vitamin C?

Another vitamin we commonly take supplements for, vitamin C, is a vital antioxidant that protects cells from damage, boosts immune function, and is essential for collagen formation. Getting enough vitamin C helps us repair our skin, bones, and blood vessels, strengthens our natural defences, increases our ability to absorb other important minerals, like plant-based sources of iron, and even helps us sleep. 

Unlike vitamin D, we can get vitamin C through lots of everyday foods. Citrus fruits, berries, peppers, broccoli, and even potatoes all contribute to our daily intake, meaning most of us in the UK can get enough vitamin C through eating a healthy, balanced diet. 

As Nutritionist Resource member and Nutritional Therapist Janet Padfield, Dip ION MBANT CNHC, explains, “Eating the real foods in their whole form is much better for us than taking supplements, as you get other nutrients and fibre from whole fruits and vegetables. But if you require supplements, take a good quality brand where you take a low dose of vitamin C two or three times daily.”

Because vitamin C is water-soluble, your body doesn’t store it in large amounts, meaning excess is usually excreted in urine. However, having very high doses regularly can cause stomach cramps, diarrhoea, and bloating. In some cases, long-term high intake can increase the risk of kidney stones. 

For most of us, vitamin C supplements aren’t necessary unless advised by a healthcare professional. Just make sure that you have a diet rich in fruit and veg to keep your vitamin C levels topped up. 

Vitamin A and toxicity: what you need to know

Supporting night vision, your immune system, and healthy skin, vitamin A is also important for normal growth and development – particularly during pregnancy. You can get vitamin A through animal products like dairy, eggs, and liver, as well as provitamin A through plant-based means, including sweet potatoes, leafy greens, red peppers and carrots. 

While essential, too much vitamin A can be harmful. Some research suggests that too much vitamin A over a long period of time can affect your bones and joints, making bones more likely to fracture when you are older. It can also include symptoms such as headaches, nausea, and blurred vision. 

It’s possible to get too much vitamin A through our diets, as well as supplements. The NHS warns that if you eat liver or liver pâté more than once a week, you may be getting too much vitamin A. As many multivitamins contain vitamin A, and common supplements like fish liver oil are also high in vitamin A, it is possible to have too much vitamin A without realising it. 

If you have been through the menopause, are an older man, or are at more risk of osteoporosis, you may need to be particularly careful about your vitamin A intake. Pregnant women may also be advised on foods to be careful about, as too much preformed vitamin A can increase risks. Check NHS guidance to see what foods to avoid or limit, or speak with your healthcare provider to find out more about what is recommended for your specific situation.

Do I really need iron supplements?

Getting enough iron helps your body to make red blood cells (vital for carrying oxygen around the body), as well as supporting your immune system, turning food into fuel, supporting cognitive health, and preventing iron-deficiency anaemia. When you don’t get enough iron, you can feel fatigued and weak, experience shortness of breath, and your immune system may be weakened.

People who menstruate – particularly those who experience heavy menstrual bleeding – are more likely to experience iron deficiency. Those with certain dietary restrictions (vegetarians, vegans), those with gastrointestinal conditions (celiac disease, ulcers), and pregnant women may also need additional iron in their diet.

There are many good sources of iron you can include as part of a balanced diet. Liver, red meat, beans, nuts, dried fruits, and fortified breakfast cereals can all be good sources of iron. 

If you are worried about low iron levels, it’s worth speaking with your GP. Iron levels are measured through a blood test, and if supplements are needed, it can be safest to undertake these under medical guidance. High doses of iron supplements can cause stomach pain, constipation, nausea and vomiting. In severe cases, excessive iron can cause serious health complications, including organ damage. 

Calcium: can you have too much?

Best known for supporting strong bones and teeth, calcium also plays an important role in supporting muscle function, nerve signalling, and heart health. We can typically get enough calcium through our diets, though some older adults or those with specific medical conditions may be advised to take supplements. Dairy products, fortified plant milks, leafy greens, and some fish all contribute to calcium intake. 

When you have too much calcium from supplements, over time, it can lead to stomach pain,  digestive discomfort, and diarrhoea. It may increase your risk of kidney stones. This can particularly be something to keep in mind if you are taking high doses of vitamin D, as this increases calcium absorption. 

As these nutrients show, the real question isn’t whether supplements are good or bad — it’s whether you actually need them in the first place.

Mind the gap: do I really need supplements?

There seems to be a supplement for everything these days. In our ever-increasing health-conscious world, it can be tempting to see supplements as a form of nutritional insurance. As we’ve seen, taking more than we need can sometimes carry risks. It’s important to make sure that you are getting targeted support, rather than guessing and hoping for the best. 

While supplements can offer support, what we need varies from person to person. Safe supplement use relies on getting the right kind of guidance and support. Your GP might recommend supplements to help with specific deficiencies. Your GP can also advise if any prescription medications you are taking may be causing symptoms you are experiencing, as well as advise on whether any supplements you are considering may interact with your prescription medication.

You can also work with a qualified nutritional professional to help support and understand your body’s needs. Taking supplements ‘just in case’ can sometimes lead to intakes that creep beyond safe levels, particularly if you are using multiple products at once. It’s not just multivitamins that impact your vitamin and mineral intake. Multivitamins, fortified foods, eating certain foods particularly high in specific vitamins and minerals (like liver), and individual supplements all contribute to your overall intake, meaning that if you have a balanced diet, you may be accidentally exceeding recommended amounts if you take supplements.

But how do you know if you’re having too much, or not enough, when it comes to the vital vitamins and minerals your body needs? Well, if you’re experiencing ongoing fatigue, low mood, hair loss, or other symptoms you think might be linked to nutrition, speak with your GP before starting any high-dose supplements. They can take symptoms into consideration, arrange for blood tests to help identify whether there is a deficiency, and rule out other potential causes.

For personalised guidance, consulting with a registered nutrition professional can help you to assess your diet, lifestyle, and health history to find any areas where there may be nutrient gaps. 

Nutrient gaps happen when you don’t get enough vitamins and minerals to meet your body’s needs. These can be small and easy to miss, or bigger and more noticeable. Even small shortages of some nutrients can cause low energy levels, poor mood, weakened immunity, and may impact your overall well-being. Some diets (for example, vegetarian or vegan) can make it harder to get enough of some vitamins, while some health conditions can also affect digestion and absorption. 

Working with a nutritional professional can help you to recognise areas that might be affecting your nutrient intake. With a little help and guidance, they can help you make small dietary adjustments that can make a meaningful difference without the need for taking supplements. They can also offer guidance for safe supplement use when it may be a beneficial option. 

Remember: The NHS advises that most of us can get the vitamins and minerals we need through eating a healthy, balanced diet. While supplements can be helpful in some circumstances for some people, they generally aren’t a substitute for eating a varied, balanced diet. 

At the end of the day, supplements aren’t a magical fix-all. They’re tools that can support our health when used thoughtfully and for the right reasons. But without guidance, it’s easy to assume more will help – when in reality, balance is what matters most. For many of us, that balance starts with varied meals, colourful vegetables, good sources of protein, and time outdoors where possible.

If you’re unsure what your body truly needs, a conversation with your GP or a registered nutrition professional can offer clarity and reassurance. A little knowledge can go a long way towards finding that healthy middle ground and ensuring your body is getting everything it needs.