There is no direct relationship between the crescent on the hand and health, and you can’t judge health by the presence or absence of the crescent, size, etc.
The crescent on the hand is the white half-moon shaped tissue of the fingernail near the root of the nail, which is in fact the newborn nail, because of its incomplete keratinization containing some water, resulting in a different refractive index showing white. The middle part of the nail grows faster and the sides grow slower, thus leading to the shape of the crescent.
The size of the crescent often represents the growth rate of the nail matrix. If the nail grows faster, the larger the crescent will be, and if the nail grows slower, the smaller the crescent will be. So there is no direct correlation between its size, presence or absence and the level of health. Certain diseases such as malnutrition and calcium deficiency may affect the growth of the nails to affect the crescent.
The crescent on your hand is not a good indicator of your health. If there is any discomfort, you should go to the hospital for treatment under the guidance of your doctor.