Symptoms of energy loss are pretty much universal, regardless of the cause.

• Confusion
• Dizziness
• Blurred vision
• Fever
• Constipation
• Dry skin
• Intolerance to cold
• Restless, disturbed sleep
• Headaches
• Weakness
• Exhaustion
• Palpitations
• Vertigo
• Feelings of muscle weakness
• Slowed movements or central nervous system reactions
• Shortness of breath.

These are all typical symptoms.

If you are taking medications (including over-the-counter medicines) these may cause similar symptoms and drowsiness too.