This is the anemia that is caused by vitamin deficiency or by malnutrition, particularly a deficiency of folic acid (B9) or vitamin B12. As suggested in the name the deficiency results in the much larger than normal but dysfunctional red blood cells-megaloblast.
Symptoms are these typically seen in anemia such as pallor/pale skin & cold hands/feet due to the lack of red blood cells, and fatigue/malaise/shortness breath/dizziness due to the lack of oxygen. The function of red blood cells is delivering oxygen to the body. Severe anemia or chronic deficiency affects nerve systems that require the most oxygen supplies. Other symptoms may include mouth pain or inflammation, stomach or GI symptoms, and may feel numbness in hand/feet.
Please go to see your doctor for diagnosis and treatments when you notice above symptoms.