Persistent Fatigue 

Feeling constantly tired or lacking energy even after adequate rest. 

Pale Skin 

Noticeable paleness of the skin, gums, or inside the eyelids. 

Shortness of Breath 

Difficulty breathing, especially during physical activity. 

Irregular Heartbeat 

Heart may beat faster to compensate for low oxygen levels. 

Weakness 

General body weakness and reduced physical strength.