Fatigue that won’t go away: causes and what to do

MedlinePlus defines fatigue as a feeling of weariness, tiredness or lack of energy. It is not the same as sleepiness, though the two often go together. Everyone gets tired after a hard week; what is worth checking is tiredness that lasts for weeks, doesn’t improve with rest or has no clear explanation.

Get evaluated if the fatigue won’t go away and you don’t know why, especially if it comes with fever, unexplained weight loss, mood changes, strong thirst or frequent urination, or loud snoring.

The table on this page sums up the most common causes. Some clues:

• Anemia: a lack of oxygen in the body makes you feel tired or weak. See anemia.
• Low vitamins: according to MedlinePlus, a lack of vitamin B12 can cause fatigue, low energy and, over time, numbness and tingling in the hands and feet. See vitamin B12 deficiency. Low vitamin D more often causes bone pain and muscle weakness or aches.
• Underactive thyroid: fatigue with weight gain, feeling cold, dry skin or mood changes. See hypothyroidism.
• High blood sugar: fatigue with strong thirst and frequent urination. See high blood sugar.
• Poor sleep: insomnia, or sleep apnea, which causes loud snoring, pauses or gasping in sleep and daytime sleepiness.
• Stress, anxiety or depression: low mood and loss of interest also feel like tiredness.
• Infections and medicines: fatigue can linger after a cold, the flu or COVID-19; with mono, according to MedlinePlus, it can last 2 to 3 months. Some medicines also cause it as a side effect.

To look for the cause of your fatigue, the doctor gives you a lab order online with the tests your case needs. The most common are:

• Complete blood count (CBC): checks for anemia. If it is low, iron tests are added.
• TSH: the thyroid test that detects hypothyroidism.
• Vitamin B12: a lack of it causes fatigue and, over time, tingling. See vitamin B12 deficiency.
• Glucose or hemoglobin A1c: check for high blood sugar or diabetes.
• Kidney and liver tests and a urinalysis, which MedlinePlus also lists.
• Early-morning testosterone, in men with low sex drive or erection problems on top of the fatigue. See low testosterone.

If along with the fatigue you feel sad, hopeless or uninterested in everything, tell the doctor: she evaluates your mood in the same visit. See also mental health care. If you have thoughts of harming yourself, don’t wait for an appointment: call Línea PAS at 1-800-981-0023 or 988, or 911.

If your sleep schedule has also drifted, see how to reset your sleep schedule; fatigue has many causes, so that does not replace an evaluation. MedlinePlus recommends:

• Getting enough sleep each night.
• Eating a balanced diet.
• Exercising regularly.
• Finding ways to relax, such as yoga, and to manage stress.
• Avoiding alcohol and drugs.

For your safety, call 911 or go to the emergency room if fatigue comes with any of these signs. See when to go to the ER.

• Chest pain or shortness of breath
• Confusion or severe dizziness
• Fainting
• Thoughts of harming yourself or suicide
• Bleeding that won’t stop, vomiting blood or black stools

Tiredness has medical causes, so see a doctor first; if work is what wears you out, THI, which runs this service, also runs a wellness retreat in Puerto Rico: read the burnout retreat guide about taking time away (it does not treat fatigue).