Some anti-seizure medication (ASM) are known to affect bone strength, and increase the risk of osteoporosis, over time. Osteoporosis is a condition of decreased bone strength (thinning of the bones) which can increase the risk of breaking a bone, particularly as you age. If you are taking AEDs for an extended period of time, your doctor may suggest that you have a bone density test, or promote exercise, diets or supplements to reduce this risk.
This is why annual review with your doctor, even if your seizures are under control, is important.