How can i break my ankle by standing on it with my other foot?

Hard to say: You are right in saying that is not a common mechanism and does not seem like enough energy to cause such an injury. Sometimes the fracture can occur in abnormal bone such as in osteoporosis or a stress fracture, or the "fracture" is not a fracture after all. Don't hesitate to seek second opinion if you are concerned that the diagnosis is not correct.

Ankle fracture: To break your ankle, you require a certain amount of force. If you apply enough force, you can break it.

Vit D levels: Hello, Many of us are deficient in Vitamin D which can affect our bone strength in the long term. This can cause stress fractures/full fractures from minor trauma. Prior to major surgeries of the foot and ankle i obtain Vitamin D levels on my patients to help me analyze bone strength and healing potential.