Feeling unusually fatigued is an early pregnancy symptom that can occur as soon as one week after you conceive. The excessive tiredness is often related to a high level of progesterone in your system, although other things such as lower levels of blood sugar, lower blood pressure, and increased blood production can all contribute.
Fatigue not related to pregnancy can be caused by stress, physical exhaustion, depression, a common cold or flu, or other illnesses. If your fatigue is related to pregnancy, it's important to make sure you get plenty of rest; eating foods that are rich in protein and iron can help offset it.
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