The alkaline earth metal used in both fireworks and medicine is strontium.

Here's why:

* Fireworks: Strontium salts, particularly strontium carbonate, are used to create brilliant red colors in fireworks.

* Medicine: Strontium ranelate is a medication prescribed for the treatment of osteoporosis, a condition that weakens bones.

Let me know if you'd like to know more about the uses of strontium!