Constantly tired? Supplements and nutrient deficiencies to check
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Can tiredness be caused by a nutrient deficiency?
Yes. Several vitamins and minerals are needed to convert food into energy and for the blood to carry oxygen. When levels are low, one of the first signals is tiredness and lack of energy. But tiredness is a non-specific symptom – it could just as easily be down to too little sleep, stress, infection or illness.
That is why the order matters: find out whether you actually have a deficiency before you start on supplements. A simple blood test at your doctor's or via a testing service gives the answer.
Nutrient deficiencies most often behind tiredness
Four deficiencies recur in medical practice when tiredness is investigated:
| Nutrient | Typical signs | Who is affected more often |
|---|---|---|
| Iron | Tiredness, breathlessness, paleness, heart palpitations | Menstruating people, pregnant women, vegans |
| Vitamin B12 | Tiredness, tingling, difficulty concentrating | Vegans, older people, those with gut conditions |
| Folate | Tiredness, anaemia, low mood | Pregnant women, one-sided diet |
| Vitamin D | Tiredness, muscle weakness, low mood | Winter months, darker skin, little sunlight |
Both B12 and iron interact, and combined deficiencies are not unusual. If you are deficient in one, it is wise to check the other too.
What does EFSA say about these nutrients?
The EU food safety authority has authorised health claims for several of them, which says something about their role in energy metabolism:
- Iron contributes to a reduction of tiredness and fatigue and to normal oxygen transport in the body.
- Vitamin B12 contributes to a reduction of tiredness and fatigue and to normal energy metabolism.
- Folate contributes to a reduction of tiredness and fatigue.
- Vitamin D contributes to normal muscle function and normal function of the immune system.
- Magnesium contributes to a reduction of tiredness and fatigue and to normal energy metabolism.
This means the substances are needed for normal energy – but only if you actually have too little. Topping up beyond your requirement will not make you more alert.
Get a blood test before starting supplements
This is the single most important piece of advice. Tiredness is too non-specific to guess at. A blood test can show:
- Haemoglobin (Hb) and iron stores (ferritin).
- Vitamin B12 and folate.
- Vitamin D (25-OH vitamin D).
- Thyroid value (TSH), since low thyroid function is a common hidden cause of tiredness.
With the results in hand, you and your doctor can target the effort where it is needed, at the right dose. Taking iron supplements without a deficiency can, on the contrary, cause stomach trouble and is not harmless at high doses.
What you can do yourself – beyond supplements
Nutrition is one piece of the puzzle. Look at the basics too:
- Sleep: regular hours and 7–9 hours. Read our tips for sleeping better.
- Stress: prolonged stress drains your energy. See what actually has support in our piece on supplements for stress.
- Food and movement: regular meals, enough protein and daily movement even out your energy.
- Alcohol and screen time: disrupt sleep quality more than many people think.
If you are a woman and notice that your tiredness tracks life stages, hormones may also play a part – read more about vitamins for women by life stage. If you specifically suspect B12, there is a deeper look at B12 deficiency and its symptoms.
When should you seek medical advice for tiredness?
Contact your doctor if the tiredness:
- Persists for several weeks despite adequate sleep.
- Comes with other symptoms such as weight loss, fever or breathlessness.
- Noticeably affects your daily life.
Behind long-term tiredness can lie anaemia, a thyroid disorder, diabetes or other conditions that need treatment. Supplements will not solve that – a proper investigation will.
Other hidden causes of tiredness
A nutrient deficiency is just one of several possible explanations. Before you blame everything on vitamins, think through:
- Sleep deprivation and an irregular body clock – the most common cause of all.
- Low thyroid function – causes sluggish tiredness, feeling cold and slowness.
- Prolonged stress – depletes your energy reserves even when you sleep.
- Low blood sugar between meals – uneven meals cause energy dips.
- Too little movement – paradoxically, sitting still makes you more tired.
Often several of these interact. That is why a broad approach – sleep, food, movement and any deficiency – gives better results than chasing a single miracle supplement.
A diet that gives steadier energy
Beyond covering any deficiencies, you can arrange your food so that energy lasts longer:
| Do this | Why it helps |
|---|---|
| Eat protein at every meal | Keeps you full longer and dampens blood sugar swings. |
| Choose whole grains over white | Provides slower, steadier energy. |
| Eat regularly | Avoids the deep afternoon dips. |
| Keep an eye on iron sources | Meat, legumes and leafy greens support oxygen transport. |
If you combine a well-thought-out diet with good sleep, you cover most of what you can influence yourself – and you quickly notice if there is something medical that needs investigating.
Frequently asked questions
Which supplement helps best against tiredness?
It depends entirely on the cause. If you have an iron deficiency, iron helps; if you have a B12 deficiency, B12 helps – but only if the deficiency is confirmed by a blood test. There is no universal supplement that makes everyone more alert. The most common causes of tiredness are iron, B12, folate and vitamin D, so start by checking those with your doctor before you buy anything.
Can I take iron supplements as a preventive measure?
No, not without a confirmed deficiency. Iron at high doses can cause stomach trouble such as constipation and nausea, and the body struggles to get rid of any excess. Only take iron supplements if a blood test shows low stores, and preferably in consultation with a doctor. Menstruating people, pregnant women and vegans are at greater risk of iron deficiency.
How quickly do you notice a difference from supplements when deficient?
It varies with the nutrient and how large the deficiency is. With iron deficiency, it can take several weeks before energy returns, since the body needs to rebuild its stores. B12 and vitamin D can also take weeks. Give the treatment time and follow up with a new test, rather than raising the dose on your own.
Can vitamin D deficiency make me tired?
Yes, tiredness is a common but non-specific sign of low vitamin D, especially during the winter months in northern climates. Vitamin D contributes to normal muscle function and immune function. If you get little sunlight, have darker skin or wear covering clothing, you are more at risk. A blood test shows whether you have a deficiency and need a supplement.