What are common nutrient deficiencies? Signs, symptoms & next steps

Do you often feel tired, run-down, or not quite yourself, even when you’re getting enough rest? Or perhaps you’ve noticed subtle changes like brittle nails, hair thinning, or low mood?

We often brush off these changes as part of a hectic lifestyle or the natural pace of ageing. But in some cases, the real culprit may be a hidden nutrient imbalance.

According to the BBC, an estimated 2 billion people worldwide aren’t getting enough essential micronutrients in their diets.

Vitamins and minerals are essential for keeping your body and mind functioning at their best. They support energy production, nerve function, bone strength, and immunity. When levels drop, the effects can show up in ways that are easy to overlook.

In this article, we’ll look at the most common deficiencies, including iron, vitamin D, vitamin B12, and magnesium. We’ll explore the signs to watch for, who’s most at risk, and outline how at-home testing and dietary changes can help you take control of your health.

Questions we’ll answer in this blog:

• What are the most common nutrient deficiencies and symptoms?
  

• Who is most at risk?
  

• Common nutrient FAQs
  

• How can you check your levels at home?
  

• What foods can help boost your intake naturally?

What are the most common nutrient deficiencies and their symptoms?

Iron

Iron plays a central role in keeping your body energised and functioning. It’s a key component of haemoglobin, the protein in red blood cells that binds to oxygen in your lungs and delivers it to tissues throughout the body. Without enough iron, your body produces fewer healthy red blood cells, which means less oxygen reaches your muscles, organs, and brain.

When this happens, everyday processes start to slow down. Your muscles fatigue more quickly, your brain may feel foggy, and even simple tasks can feel exhausting. Over time, this lack of oxygen circulation can lead to widespread symptoms like persistent tiredness, shortness of breath, dizziness, or headaches.

In short, iron is the mineral that keeps your cells fuelled with oxygen. Without it, your body struggles to produce the energy you need to function at your best.

The NHS indicates that some common signs of low iron include:

• Persistent tiredness that rest doesn’t fix
  

• Pale skin
  

• Shortness of breath or dizziness
  

• Cold hands and feet
  

• Brittle nails or hair loss

Who is at risk?

• Women of childbearing age (due to menstruation)
  

• Pregnant women
  

• Vegetarians and vegans
  

• People with gastrointestinal conditions affecting absorption (e.g., coeliac disease)
  

• Frequent blood donors
  

For those in higher-risk groups or who have noticed some of these symptoms, an at-home test can be a helpful first step toward understanding your nutrient status more clearly and can provide useful context for a discussion with a healthcare professional.

Vitamin D

Vitamin D is often known for its role in building and maintaining strong bones, but its benefits go far beyond skeletal health, influencing hundreds of processes in the body. Vitamin D supports the immune system by helping your body fight infections, and it plays an important role in regulating mood and cognitive function, with low levels often linked to feelings of fatigue or low mood.

Despite its importance, vitamin D deficiency is widespread. Unlike most vitamins, you can’t rely solely on food to meet your needs; your body primarily produces vitamin D through direct sunlight on the skin.

Without enough vitamin D, bones can become weaker over time, and the immune system may not function as effectively.

Possible signs of deficiency include:

• Low mood or mood changes
  

• Muscle aches or weakness
  

• Persistent fatigue
  

• Frequent colds or infections
  

Who is at risk?

According to the NHS, people who are at a higher risk of a vitamin D deficiency include:

• People with limited sun exposure
  

• Those who spend most of their time indoors
  

• People with darker skin tones (reduced vitamin D synthesis)

If you’ve noticed some of the signs mentioned or simply fall into a group more likely to have low levels, a vitamin D check can offer helpful insight into how well your current routine supports your overall well-being.

Vitamin B12

Vitamin B12, or cobalamin, is a powerhouse nutrient that plays a key role in energy production, nerve protection, and DNA synthesis. It helps your body make healthy red blood cells and is vital for maintaining the protective sheath (myelin) that surrounds nerves. Without adequate B12, communication between your brain and body becomes less efficient, which can lead to tingling sensations, memory lapses, or even mood changes.

Because B12 is found almost exclusively in animal products like meat, fish, eggs, and dairy, vegetarians and vegans are especially at risk of deficiency. Even people who consume these foods can develop low B12 due to poor absorption.

The NHS suggests that some signs of deficiency include:

• Tingling or numbness in the hands and feet
  

• Memory issues or brain fog
  

• Muscle weakness
  

• Indigestion
  

• Persistent fatigue
  

Who is at risk?

• Vegetarians and vegans
  

• Older adults (reduced stomach acid and absorption with age)
  

• People with digestive disorders (e.g., Crohn’s disease, coeliac disease)
  

• Individuals taking certain medications (e.g., metformin, proton pump inhibitors)
  

• Those who have undergone gastric surgery
  

For anyone at higher risk, staying mindful of these symptoms is a helpful way to keep in tune with your body’s needs and adjust your diet where possible.

Magnesium: the relaxation mineral

Magnesium is involved in over 300 chemical reactions in the body, making it one of the most versatile and vital minerals. It supports muscle and nerve function, regulates blood sugar and blood pressure, and contributes to strong bones and DNA repair.

When magnesium levels are low, the effects can ripple through your body in surprising ways. You might notice muscle cramps, headaches, restless sleep, or even heightened stress and irritability. Over time, chronic low magnesium has been linked to higher risks of heart disease, type 2 diabetes, and osteoporosis.

Modern diets, often high in processed foods but low in leafy greens, nuts, seeds, and whole grains, are a significant factor in widespread magnesium deficiency. Stress and certain medications can also deplete magnesium further. Making dietary adjustments or considering supplementation (if advised) can help restore balance and improve both physical and emotional well-being. 

According to Metabolic Support UK, possible signs of low magnesium include:

• Muscle cramps or twitches
  

• Vertigo
  

• Mood changes or irritability
  

• Palpitations
  

Who is at risk?

• People under chronic stress
  

• Those with diets low in leafy greens, nuts, seeds, and whole grains
  

• Individuals with gastrointestinal conditions (e.g., Crohn’s disease)
  

• People with type 2 diabetes or insulin resistance
  

• Heavy alcohol consumers
  

• Individuals taking certain medications (e.g., diuretics, proton pump inhibitors)

Keeping an eye on these symptoms if you’re in a greater risk category can help you stay connected to your body’s signals and make supportive changes to your diet when needed.

Frequently asked questions about nutrient deficiencies

Can stress cause nutrient deficiencies?

Yes. Chronic stress can increase the body’s demand for specific nutrients, particularly magnesium and B vitamins, which are essential for energy production and nervous system balance. At the same time, stress can interfere with digestion and absorption, meaning you may not use the nutrients you eat as efficiently.

When stress hormones like cortisol remain elevated for long periods, your body may burn through magnesium and B vitamins more quickly. Over time, this can contribute to symptoms like low energy, poor sleep, irritability, or digestive issues. That’s why supporting nutrient intake, alongside stress management strategies, is essential for overall resilience.

Do nutrient deficiencies always cause noticeable symptoms?

Not always. Some deficiencies develop gradually and may only cause subtle signs, such as tiredness, poor sleep, or mood changes. For some people, these symptoms may be brushed off as ‘just stress’ or ‘normal fatigue’. Others may not notice any apparent symptoms until the deficiency becomes more significant.

For example, iron deficiency can cause noticeable fatigue, paleness, or shortness of breath, but in early stages, the only sign may be feeling more tired than usual. Similarly, low vitamin D may not cause immediate symptoms, but over time, it can contribute to bone, immune, or mood changes.

This is why proactive testing can be so helpful: it helps identify deficiencies before they progress to more severe or harder-to-reverse problems.

How quickly can deficiencies be corrected?

It depends on both the nutrient and the severity of the deficiency. Some nutrients, like vitamin D, can improve relatively quickly with safe sun exposure and supplementation. However, the NHS states that some nutrients, like iron or vitamin B12, may take weeks to months of consistent supplementation to restore healthy levels.

Correction also depends on the form of the nutrient (for example, iron supplements are absorbed at different rates depending on the type) and your individual health. People with digestive conditions that reduce absorption, such as celiac disease or inflammatory bowel disease, may need longer to restore levels.

In general, steady progress is expected with the proper diet or supplementation plan, and follow-up testing helps confirm when levels have returned to a healthy range.

Diet can play a powerful part in supporting your nutrient intake, with the following foods being great for boosting specific nutrients:

• Iron: lean red meat, poultry, lentils, beans, spinach, fortified cereals
  

• Vitamin D: salmon, mackerel, egg yolks, fortified dairy or plant-based milks (plus safe sun exposure)
  

• Vitamin B12: meat, fish, eggs, dairy, or fortified plant-based foods like nutritional yeast
  

• Magnesium: leafy greens, nuts, seeds, whole grains

Key takeaways

• Nutrient deficiencies can mimic everyday stress or fatigue.
  

• The most common gaps are iron, vitamin D, vitamin B12, and magnesium.
  

• At-home testing is a fast, convenient way to understand your health.
  

• A balanced diet rich in whole foods is your best defence.

Take charge of your well-being

Feeling tired, low, or off-balance doesn’t have to be your normal. Often, your body is sending signals that something’s missing.

At-home nutrient testing offers a simple way to check your levels, get clarity, and make informed choices about your diet, lifestyle, or next steps with a healthcare professional.

At Rezure, we believe health insights should be clear and accessible. By paying attention to your body’s signals and taking proactive steps, you can support your energy, mood, and overall vitality.

Could your symptoms be linked to nutrient deficiencies? Explore our range of at-home nutrient tests today and take the first step toward feeling your best.