Don't worry too much.
This is not calcium deficiency. Calcium deficiency is characterized by cramps in hands and feet and weakness in limbs, rather than convulsions during sleep.
To understand this problem, let's take a look at an example: many athletes shake their hands and feet to relax their muscles after strenuous exercise, especially when they are anaerobic (referring to training and sports that need to hold their breath, such as weightlifting and dumbbells). Shaking muscles helps to release lactic acid (a substance that makes people feel sore) accumulated in muscle tissue after strenuous exercise.
Similarly, we should know that sleep is not just a brain phenomenon, it is a physiological phenomenon that requires the whole body to participate. During sleep, people's sensory organs, such as ears, nose and nerves in various parts of the skin, are in a very dull state. Muscle tissue also needs "sleep". This is manifested in the relaxation of muscle depth (you can do a small experiment and clench your fist when you wake up in the morning, hehe, isn't it a bit ineffective? )。 When sleeping, all aspects of the body are gradually relaxing, and muscles are no exception. When muscles relax to a certain extent, they will twitch on their own, just like athletes shaking their hands and feet, and their function is to make muscles reach a state of deep relaxation.
So this kind of limb twitching during sleep is normal, and it is more likely to happen at night when you are tired during the day.