Some factors that contribute to excessive tiredness include:

1. Poor sleep habits. Inconsistent or irregular sleep patterns; trying to function on too little sleep; taking long naps throughout the day; taking naps too close to bedtime.

2. Dietary factors. There are certain foods that make us feel more sleepy. These include candy, pop and desserts, peanuts and peanut butter, dairy products, turkey, bananas and apples. Also having a late lunch seems to contribute to mid-afternoon sleepiness.

3. Crash diets and weight loss pills may cause sleep abnormalities, which leave you feeling tired and drained.

3. Sedating drugs and alcohol. This includes many prescribed and over the counter medications. Also, not following the instructions properly can lead to bouts of sleepiness. This includes not paying proper attention to timing and dosages.

4. Having the cold or flu, or suffering from a minor infection, or an autoimmune disease.

5. Feeling anxious or depressed saps and drains your energy.

6. Having your period. Some women also report feeling more tired and sleepy just before their period or during ovulation.

7. Being physically active. This uses up our energy reserves.

8. Doing boring, monotonous, repetitive tasks.