We all have days when we feel tired. A late night, a stressful week or a busy schedule can leave anyone reaching for another cup of coffee. 

But if you're waking up exhausted, relying on caffeine to get through the day, or finding your energy levels have been low for weeks or months, it's worth paying attention. 

While poor sleep, stress, hormone changes and certain medical conditions are common causes of fatigue, nutrient deficiencies also play a significant role, more so than we think. Your body relies on vitamins and minerals to produce energy, transport oxygen, support your thyroid, maintain healthy muscles and keep your brain functioning at its best (1). 

The important thing to remember is that fatigue is a symptom for something that is happening within the body, it’s not a diagnosis, nor is it the body asking for another cup of coffee. Rather than reaching for supplements in the hope they'll fix the problem, it's important to identify the underlying cause and deal with what’s going on beneath the surface.  

1. Could I be Iron deficient? 

Iron is one of the most common nutrient deficiencies worldwide and a leading nutritional cause of fatigue (10). It’s also the nutrient that we automatically associate with feeling run down, as women, after our cycle. 

So why do we think of Iron in fatigue? Iron is essential for producing haemoglobin, the protein in red blood cells that carries oxygen around the body. Without enough iron, your muscles and organs receive less oxygen, which can leave you feeling exhausted and weak (1). 

A 2017 meta-analysis found that iron supplementation significantly improved fatigue in people with iron deficiency, even when anaemia was not present, highlighting that low iron stores alone can affect the way we physically feel when it comes to our wellbeing and vitality. (2). 

Pairing iron-rich foods with a source of vitamin C, such as citrus fruit, peppers, or berries, can significantly boost how much iron your body absorbs, making it a simple way to get more from your diet. 

Before taking supplements: Iron supplements should only be taken if a deficiency has been confirmed by a blood test or advised by your GP or healthcare professional. Too much iron can be harmful, and persistent iron deficiency should always be investigated to identify the underlying cause (8). 

2. Vitamin B12 

Vitamin B12 helps make red blood cells, keeps your nerves healthy and turns food into energy (1). It's found almost exclusively in animal foods, so it can't be reliably obtained from a vegan diet without fortified foods or a supplement. 

The body stores B12, so a deficiency can take months or even years to show up. Symptoms tend to creep in gradually and are easy to miss until levels are already low. 

If you notice numbness, tingling or problems with balance, speak to your GP promptly. A simple blood test can check your B12 status, and treatment will depend on what's causing the deficiency (5,6). 

3. Folate (Vitamin B9) 

Folate works closely with vitamin B12 to produce healthy red blood cells and support DNA production (1). 

Low folate can contribute to megaloblastic anaemia which can show up as fatigue, weakness and poor concentration. Folate deficiency should always be assessed alongside vitamin B12 deficiency because both deficiencies can occur together (5). 

4. Vitamin D 

Vitamin D, the supplement we suddenly forget we’re supposed to be taking in the autumn and winter months. Supporting bone health, muscle function and immune health, it may not directly involved in energy production but low vitamin D status is been associated with fatigue, muscle weakness and reduced wellbeing in some people (7). 

Vitamin D also plays a role in regulating mitochondrial function, the process by which cells generate energy, which may help explain why deficiency is so often linked with low energy and heavy limbs rather than a specific, easily named symptom (7). 

In the UK, adults are advised to consider taking a daily vitamin D supplement during autumn and winter because sunlight exposure is often insufficient for adequate vitamin D production (7). Skin makes vitamin D from direct sunlight, and between around October and early March, the UK sun sits too low in the sky for this to happen effectively, regardless of how much time is spent outdoors.  

Vitamin D3 (cholecalciferol) is the form your skin makes from sunlight, and research shows it raises and maintains blood levels of vitamin D more effectively than D2 (ergocalciferol), the plant-derived form. Because vitamin D is fat-soluble, how you take it matters too. It's absorbed best alongside dietary fat, which is why many formulas pair it with omega-3 or suggest taking it with a meal. It's also often paired with vitamin K2, but for a different reason. K2 doesn't boost absorption. Instead, it activates the proteins that help direct calcium into bones and teeth and away from soft tissues such as arteries (3). Together, they make a smarter, more complete approach to vitamin D. 

 Some groups are advised to consider a supplement all year round, including those with limited sun exposure, darker skin, or who cover most of their skin when outside (7). 

As with iron, it's worth having levels checked via a blood test if fatigue is persistent, since both very low and excessively high vitamin D levels can affect wellbeing, and supplementation should be tailored to what's actually needed. 

5. Magnesium 

Magnesium is involved in more than 300 enzyme reactions throughout the body, including many involved in converting food into usable energy (ATP) (1). 

Although severe magnesium deficiency is uncommon, inadequate intake may contribute to fatigue, muscle cramps and poor sleep. A food-first approach is recommended before considering supplementation unless deficiency is suspected or confirmed (1,9). 

Not all forms of magnesium behave the same way in the body, and the right one often depends on what you're using it for: 

Magnesium glycinate is gentle on the stomach and well absorbed, and is often favoured for sleep, stress and anxiety support. 

Magnesium citrate is also well absorbed but has a natural laxative effect, making it a common choice for occasional constipation as well as general supplementation. 

Magnesium malate is easy to digest and is often associated with energy support, since malate itself plays a role in the body's energy-producing pathways. 

Magnesium L-threonate is a newer form able to cross the blood-brain barrier, and is being studied for its potential role in memory and cognitive support. 

Magnesium taurate is typically used to support heart health and healthy blood pressure. 

Magnesium oxide is poorly absorbed relative to other forms and is generally used for short-term constipation relief rather than for correcting a deficiency. 

As a general rule, if fatigue or sleep is the main concern, glycinate or malate tend to be better suited than oxide, which is absorbed far less efficiently by the body. It’s also the combination we have formulated into Essential Magnesium. With many of us utilising our Magnesium stores quite quickly in our fast paced, active lifestyles, glycinate and malate are the two that we often burn through the quickest.  

6. Iodine