Vitamin and Mineral Deficiencies and Fatigue: A Complete Guide

Key takeaways

• Iron, vitamin B12, vitamin D, magnesium, and folate are the nutrients most consistently linked to fatigue, but each affects energy through a different mechanism.
• Certain groups are more likely to run low: people on restrictive diets, those with heavy menstrual periods, pregnant people, older adults, people with digestive conditions, and people on certain long-term medications.
• A blood test can usually check the nutrients most relevant to fatigue — but which ones to test depends on your situation, so it’s worth asking a clinician rather than guessing.
• Dehydration and electrolyte imbalance are a separate but related cause of low energy, distinct from vitamin or mineral deficiency in the classic sense.
• Most everyday tiredness is not caused by a vitamin deficiency, and taking high-dose supplements "just in case" is not a safe shortcut — some vitamins and minerals are harmful in excess.
• Food sources are generally the preferred first step for most people; supplements are best used to correct a confirmed, tested deficiency under professional guidance.

Common symptoms

• Persistent tiredness that doesn’t fully improve with rest or sleep
• Feeling weak or lacking stamina during normal daily activities
• Pale skin, brittle nails, or hair changes (sometimes associated with low iron)
• Pins-and-needles sensations, numbness, or balance problems (sometimes associated with low vitamin B12)
• Low mood, irritability, or difficulty concentrating
• Muscle cramps, twitches, or weakness (sometimes associated with low magnesium)
• Shortness of breath or a noticeably fast heartbeat with mild exertion
• Headaches or dizziness, particularly when standing up quickly

Possible causes

• Not eating enough of a nutrient — for example, a diet low in iron-rich or vitamin B12-rich foods
• Reduced absorption from the digestive tract, even when food intake looks adequate
• Digestive conditions such as celiac disease or inflammatory bowel disease that damage the gut lining
• Bariatric (weight-loss) surgery, which changes how the stomach and intestines absorb nutrients
• Blood loss, including heavy menstrual periods or slow, hidden bleeding in the digestive tract
• Increased nutrient needs, such as during pregnancy or breastfeeding
• Long-term use of certain medications, such as acid-reducing drugs that lower vitamin B12 absorption over time
• Reduced stomach acid or changes in digestion that come with older age, which can lower absorption of vitamin B12 and other nutrients

Nutrients linked to fatigue at a glance

Several nutrients are consistently linked to low energy when levels run low. The table below summarizes the ones most often discussed, in plain terms — what each one does for energy, who tends to be more at risk of running short, and where it’s commonly found in food. This is a starting point for a conversation with a healthcare professional, not a checklist for self-diagnosis.

How a nutrient shortfall actually drains your energy

It helps to understand, in simple terms, why these particular nutrients matter so much for energy. Iron is a core building block of hemoglobin, the protein in red blood cells that carries oxygen from your lungs to the rest of your body. When iron is low, your body makes fewer or smaller red blood cells, so tissues — including muscles and the brain — receive less oxygen than they need to function well.

Vitamin B12 works differently. It’s needed to keep the protective coating around nerves healthy and to help red blood cells develop normally. A long-standing shortfall can affect both the nervous system and the blood, which is why low B12 is sometimes linked not just to fatigue but also to tingling, numbness, or difficulty concentrating.

Magnesium is involved in the chemical reactions that cells use to produce usable energy, and it also plays a role in muscle and nerve function, so a shortfall can show up as tiredness alongside cramps or muscle twitches. Folate, like B12, supports healthy red blood cell production. Vitamin D’s link to fatigue is less direct and less well understood than iron or B12, but it plays a role in muscle function and has been associated with low energy in some people.

Who is more likely to run low

Nutrient shortfalls aren’t random — certain circumstances make them more likely. Diet is one of the biggest factors: people following a vegan or vegetarian diet without deliberate planning can run low on vitamin B12, iron, or both, since these are more concentrated in animal foods. Very low-calorie diets or highly restrictive eating patterns of any kind can fall short on several nutrients at once simply because there isn’t enough food volume to cover the body’s needs.

Blood loss is another major factor. Heavy menstrual periods are a common and often under-recognized cause of low iron in people who menstruate. Pregnancy increases the body’s demand for iron, folate, and other nutrients substantially.

Age and digestive health matter too. As people get older, the stomach tends to produce less acid, which is needed to release vitamin B12 from food — so older adults are more likely to become B12-deficient even on a varied diet. Digestive conditions such as celiac disease or inflammatory bowel disease can damage the part of the gut where nutrients are absorbed, and bariatric surgery permanently changes the digestive tract in ways that reduce absorption of several nutrients. Finally, some medications interfere with nutrient absorption over long-term use — long-term use of acid-reducing medications, for example, can gradually lower vitamin B12 absorption.

Can I just take a multivitamin?

This is one of the most common questions, and the honest answer is: it depends. A general multivitamin is unlikely to cause harm for most healthy adults when used as directed, but it’s also unlikely to meaningfully fix a specific, significant deficiency — the doses in most multivitamins are designed for general maintenance, not for correcting a confirmed shortfall. If a blood test shows you’re genuinely low in a particular nutrient, a healthcare professional may recommend a targeted, higher-dose supplement for that specific nutrient.

It’s also important to understand that more is not automatically better. Some vitamins and minerals are fat-soluble or otherwise capable of building up in the body, and taking high doses without medical supervision can cause harm. Vitamin A, vitamin D, and iron are three well-known examples: excess vitamin A has been linked to liver and bone problems, excess vitamin D can raise calcium to unsafe levels, and excess iron can build up in organs and is particularly risky in high doses. Do not take a specific supplement dose based on general information like this — always ask a healthcare professional about which nutrients to test and what dose and duration make sense for you.

A reasonable general approach is: food sources first where possible, testing before assuming a specific deficiency, and supplementation as a targeted response to a confirmed and tested shortfall rather than a blanket "just in case" habit.

Hydration and electrolytes: a related but different story

Water and electrolytes — minerals like sodium, potassium, and chloride that carry an electrical charge in the body — aren’t vitamins, but they’re often grouped into the same conversation about nutrition-related fatigue. Even mild dehydration can cause tiredness, headache, difficulty concentrating, and dizziness, sometimes within just a few hours of inadequate fluid intake, especially in hot weather, during illness with vomiting or diarrhea, or during intense physical activity.

Electrolytes work alongside water to help nerves and muscles function and to keep fluid balanced between the inside and outside of cells. An imbalance can also cause fatigue, muscle cramps, or an irregular heartbeat. Unlike most vitamin or mineral deficiencies, hydration and electrolyte problems can sometimes develop and resolve quickly, but they can also become medically serious, so persistent symptoms — especially with vomiting, diarrhea, heat exposure, or heavy sweating — are worth discussing with a healthcare professional.

What this does not mean

It’s worth being direct about this: most everyday tiredness is not caused by a vitamin or mineral deficiency. Sleep quality and quantity, stress, physical activity levels, underlying medical conditions, mental health, and simply the demands of daily life are far more common contributors to fatigue than a nutrient shortfall. Nutrient deficiencies are a real and testable possibility worth ruling in or out, not the default explanation for feeling tired.

Because of this, "over-supplementing just in case" is not a safe or effective shortcut. Taking high doses of vitamins or minerals without a confirmed deficiency doesn’t reliably improve energy in people who aren’t actually deficient, and for some nutrients — particularly fat-soluble vitamins and iron — it can cause harm. If fatigue persists, the more useful path is usually a conversation with a healthcare professional about your overall health picture.

What blood testing usually looks at

When a clinician suspects a nutrient shortfall might be contributing to fatigue, they typically start with a blood test, since it’s a straightforward way to check several relevant markers at once. Commonly checked markers include ferritin (a protein that reflects how much iron is stored in the body), vitamin B12, folate, and vitamin D level, sometimes alongside a general blood count and other tests depending on your symptoms and history.

Which of these are actually relevant to you depends on your diet, symptoms, medical history, and risk factors — not everyone needs every test. This is exactly the kind of decision best made with a healthcare professional, who can weigh your individual situation and order the tests that make sense.

Self-care guidance

These low-risk steps may help but are not a treatment plan. Speak with a healthcare professional before starting supplements or stopping medication.

• Aim for a varied diet that includes iron-rich foods (meat, beans, leafy greens), vitamin B12 sources (animal products or fortified alternatives), and a range of fruits, vegetables, nuts, and whole grains
• If you follow a vegan or vegetarian diet, learn which nutrients need extra attention, particularly vitamin B12, iron, and vitamin D, and consider discussing fortified foods or supplements with a healthcare professional
• Stay adequately hydrated throughout the day, and increase fluids during hot weather, illness, or intense exercise
• Keep track of your symptoms, diet pattern, and any risk factors so you can describe them clearly to a healthcare professional
• Avoid starting high-dose vitamin or mineral supplements on your own, especially iron, vitamin A, or vitamin D, without testing first
• If you’re prescribed a supplement for a confirmed deficiency, take it as directed and attend any follow-up testing
• Prioritize sleep, movement, and stress management alongside nutrition, since these often have at least as much impact on energy levels

When to see your doctor

• Fatigue that has lasted more than a couple of weeks without an obvious explanation
• You follow a restrictive diet and are concerned you may not be getting enough of certain nutrients
• You have heavy menstrual periods, are pregnant, or have a digestive condition and haven’t discussed nutrient monitoring with a clinician
• You take long-term medication (such as an acid reducer) and want to know if periodic nutrient checks make sense for you
• You’re considering starting a vitamin or mineral supplement and want guidance on whether testing should come first

Frequently asked questions

Conclusion

Vitamin and mineral deficiencies are a genuine, well-documented cause of fatigue, but they’re one possibility among many, not the default explanation for feeling tired. Iron, vitamin B12, vitamin D, magnesium, and folate each support energy through a different mechanism, and certain groups — including people on restrictive diets, those with heavy periods, pregnant people, older adults, and people with digestive conditions — are more likely to run low. If fatigue persists, the most reliable next step is a conversation with a healthcare professional about whether testing makes sense for you, rather than assuming a deficiency or reaching for high-dose supplements without knowing your levels first.

References

Public health sources are listed in this order: USA, UK, Canada, Australia.

Explore this topic further

Related articles