Constant fatigue and weakness: anemia and other causes, which doctor to see
Fatigue that does not lift after a weekend or a vacation is not laziness and not "just age". Behind it often stand anemia, thyroid problems, vitamin deficiency, sleep apnea or depression. Start with a general practitioner and basic tests.
Common causes
- Anemia (low hemoglobin), most often caused by iron deficiency
- An underactive thyroid
- Vitamin D and B12 deficiency
- Chronic sleep deprivation and sleep apnea
- Depression and burnout
- Recent infections
- Diabetes
When to seek urgent help
Do not wait for a scheduled visit if you have any of these signs:
- Fatigue with unexplained weight loss
- Fatigue with shortness of breath and pallor
- Fatigue with fever for more than a week
- Fatigue with intense thirst and frequent urination
- Fatigue with low mood and thoughts of self-harm — help is needed now, call 103
Ambulance: 103 (103 from a mobile) · Unified rescue service: 911
Your specialist
General practitioner
What to bring to the visit
- A description: how long you have felt tired, whether it changes during the day
- A sleep diary for a week
- Previous test results
- A list of medicines and supplements you take
Frequently asked questions
What is anemia and what are its signs?
Anemia is a condition in which the hemoglobin in the blood is low and the organs get less oxygen; typical signs are weakness, tiring easily, pale skin, shortness of breath and a pounding heartbeat with ordinary activity, and dizziness. A complete blood count detects it; take the result to a general practitioner, who will look for the cause, most often iron deficiency. If tiredness comes with shortness of breath and pale skin, do not wait for a routine appointment: this is one of the signs in the “When to seek urgent help” list.
Low hemoglobin or ferritin: which doctor should I see?
A general practitioner, or a pediatrician for a child. Hemoglobin shows whether there is anemia and ferritin shows the body's iron stores; the doctor will compare the results with how you feel and look for the cause. When iron is low, in adults it is often due to heavy periods or hidden bleeding in the stomach or bowel, so the doctor may refer you to a gynecologist or gastroenterologist and, if needed, to a hematologist.
What tests are usually ordered for fatigue?
Most often — a complete blood count, ferritin, TSH (thyroid), glucose, vitamin D and B12. The exact list is decided by the doctor at the visit.
Low vitamin D or B12: which test and which doctor?
Both are checked with a blood test. Take the results to a general practitioner: they will decide whether the deficiency needs correcting and, for low vitamin B12, look for the cause, for example a stomach or bowel condition or a diet without animal products. Do not take high doses of vitamin D without a doctor: a long-term excess is harmful too.
Can fatigue come from the thyroid?
Yes: with an underactive thyroid (hypothyroidism), common complaints are severe tiredness, feeling cold, weight gain and constipation. It is checked with a TSH blood test; if the result is outside the normal range, see an endocrinologist.
Can fatigue be "just nerves"?
Yes, burnout and depression are common causes. If the tests are normal, discuss it with a psychotherapist: it is just as real and just as solvable.
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The information on this page is for reference only and does not replace a doctor's consultation. Only a doctor can make a diagnosis in person. If your condition worsens, call 103.