Young children typically demonstrate a "start-stop" pattern of activity, where one moment they are going at top speed, followed by a period of utter exhaustion. It's normal for this pattern to repeat several times per day, according to Dr. Trisha Macnair in her 2009 article about tiredness for the BBC news. Sudden fatigue may not be of serious concern, however, look for other symptoms and possible triggers, and talk to your child's doctor.
Possible Causes
While most fatigue is normal, other causes can include sleep disturbance, psychological problems or the onset of illness. Almost any illness can cause tiredness in children, but the most common are infections. Children have frequent coughs, colds and respiratory infections, which usually causes a few days of fatigue, according to Macnair. "Occasionally, especially after a bacterial throat infection, tiredness can persist, sometimes resurfacing intermittently for several weeks," writes Macnair.
Sleeping Environment
Look for symptoms during your child's day, including recording sudden bouts of fatigue. See if you can find any triggers. Most young children need in excess of 10 hours of sleep per night. Check if your child is getting enough sleep time without interruption from brothers, sisters or pets. If your child is not following a regular sleep schedule, it could help to keep a regular bed time.
Nutrition
If tiredness is a problem right before meals, your child's blood sugar could be dipping. To alleviate fluctuations in blood sugar, try healthy in-between-meal snacks. You may also want to try vitamin supplements, especially if your child is not eating adequate amounts of fruits and vegetables.
Other Conditions
Talk to your pediatrician if you are concerned about your child's sudden fatigue, as, in rare cases, it can be an indication of a more serious condition, such as diabetes or cancer. Stay informed of other symptoms, such as excessive thirst or weight loss, which may indicate diabetes. Acute and sudden muscle weakness and loss of function in one area of the body may indicate a problem within the brain.
