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Autumn fatigue and nutritional deficiency may feel similar, but differ in the body's signals. While seasonal fatigue mainly affects motivation and sleep needs, nutritional deficiency often causes physical symptoms such as shortness of breath, palpitations, dizziness or numbness. Since hidden deficiencies in iron, B12, folate or vitamin D – as well as thyroid problems – require specific action, a targeted blood test is the safest way to find the right treatment instead of guessing with supplements.
Colder mornings, darker afternoons and a body that feels sluggish even before the week has started. Many people call it autumn fatigue. Sometimes that's true. But sometimes fatigue is the body's way of signaling that something is missing, for example iron, vitamin B12 or vitamin D. The difference is not always noticeable in the mirror, but it can often be seen in a blood test.
When is fatigue normal - and when should you suspect a nutritional deficiency?
Fatigue during autumn is common. Shorter days can affect circadian rhythm, sleep quality and energy, and stress or lack of sleep are common explanations when energy fails. Low mood and seasonal depression can also cause a noticeable lack of energy.
What speaks more in favor of nutritional deficiency is that the fatigue does not really fit the situation. You may sleep but still wake up feeling unwell, become unusually short of breath on stairs, have palpitations, feel dizzy or notice that your concentration is failing in a new way. Then it is not enough to blame everything on the darkness.
A practical way to think is to ask yourself: Has something changed in your body, or just in the season? If you used to get a little tired in October but now you can barely exercise, work or recover from everyday activities, the cause should be investigated more broadly.
Common deficiencies that can cause fatigue in the fall
The most common deficiency behind fatigue is iron deficiency, sometimes with anemia, so-called anemia. Hemoglobin is the substance in red blood cells that transports oxygen. If iron stores are low, it becomes more difficult for the body to form enough functioning red blood cells, and then you may feel tired, pale, short of breath or have palpitations. Heavy menstruation is a common cause, but iron deficiency can also occur without heavy menstruation.
A deficiency in vitamin B12 can also cause fatigue, but often in a slightly broader way. In addition to a lack of energy, you may experience tingling or numbness in the feet and hands, a burning sensation on the tongue, unsteady walking or memory problems. B12 deficiency often develops slowly, which means that many people get used to the symptoms before seeking help.
Folate deficiency can cause similar problems to B12 deficiency because both are needed for blood formation. This means that fatigue, paleness and reduced energy can sometimes be due to more than one deficiency at the same time. Therefore, it is wise not to guess with single supplements if the symptoms have become clear.
Vitamin D is often associated with autumn and winter, but the deficiency does not usually primarily cause "sleepy" fatigue. It is rather associated with muscle weakness, diffuse pain and, in the long term, effects on the skeleton. In Sweden, vitamin D supplements are recommended for certain risk groups, especially during the winter months, for example people who rarely spend time in the sun or do not eat fish and vitamin D-fortified foods.
What symptoms speak more of a deficiency than of regular autumn fatigue?
Autumn fatigue is usually about you being more sluggish, wanting to sleep more and feeling a little less motivated when the days get darker. Nutritional deficiency often gives several bodily signals at the same time. It is the combination that raises suspicion.
Signs that should make you think about taking a test are, for example:
- fatigue that does not improve despite sleep and recovery
- pallor, shortness of breath or palpitations with light exertion
- dizziness, headache or lower physical strength than usual
- tingling, numbness or balance problems
- stinging on the tongue, cracks in the corners of the mouth or unexplained lack of concentration
- muscle weakness or diffuse bone and muscle pain
A common question is whether you can have iron deficiency without having a low blood percentage. Yes, you can. Iron stores can be depleted before the hemoglobin drops significantly. Therefore, someone may feel unusually tired even though a simple Hb test alone does not capture the whole picture. A single blood test is rarely enough to assess everything, without the test results needing to be interpreted together with symptoms and sometimes with more analyses.
Who is at greater risk of nutritional deficiency?
People with heavy periods are in a clear risk group for iron deficiency. The same applies to those who have recently been pregnant, do a lot of endurance training, eat one-sidedly or have had long-term gastrointestinal problems. For example, if you bleed a lot every month and at the same time notice that you become short of breath from things that you previously could easily do, iron deficiency is a reasonable suspicion.
B12 deficiency is more common in people who eat a completely vegan diet without supplements, but also in cases of impaired absorption in the stomach or intestines. Autoimmune conditions, inflammation of the gastric mucosa and certain intestinal diseases can cause the body to not absorb the vitamin properly. Symptoms can then occur even though the diet seems adequate.
The risk of vitamin D deficiency is higher if you rarely spend time in the sun during the summer, wear full-covering clothing outdoors or avoid both fish and vitamin D-fortified foods. Anyone over 75 is also recommended to take a higher daily supplement than younger adults. It can be difficult to reach the recommended intake of vitamin D in the Swedish population.
Other causes of fatigue must also be included in the picture. Hypothyroidism, i.e. low metabolism, can cause fatigue, chills and depression. Depression and prolonged sleep deprivation can cause similar symptoms to deficiency states and sometimes several causes occur at the same time.
What should you test if you suspect a nutritional deficiency?
If the issue is autumn redness or nutritional deficiency, you often need to start with regular blood tests. In suspected iron deficiency, hemoglobin and iron status are central, often together with ferritin, which reflects the body's iron stores. If a B12 or folate deficiency is suspected, these vitamins are checked, and sometimes additional tests are needed depending on symptoms and previous illnesses.
In the case of prolonged fatigue, it is also reasonable to think more broadly than just vitamins and minerals. Thyroid tests may be relevant if you are also feeling cold, have dry skin, or are constipated. In some cases, it is also necessary to assess blood sugar, inflammation or kidney function depending on the overall picture. This is precisely why sampling becomes more useful than trying several different supplements at random.
Another important patient question is whether you can start treating yourself right away. For some, especially with low risk and mild symptoms, a regular vitamin D supplement may be reasonable because However, in the case of clear fatigue, neurological symptoms or suspected anemia, the cause should be determined first. This is especially true for B12 deficiency, where nerve damage may require prompt assessment and treatment.
Fatigue is a non-specific symptom, but that's precisely why it deserves precision. A blood test doesn't just help you find a deficiency. It can also help you stop chasing the wrong explanation, whether the answer lies in iron stores, vitamin levels, the thyroid, or something else entirely.
