Dear Mary: I’m a few months from my Medicare birthday, when I’ll turn 65. I have had a high-deductible health savings account qualified insurance plan for more than 10 years. The health savings account has a decent balance of nearly $15,000 because I’ve enjoyed good health and few medical expenses. My question: Can I keep my health savings account once I’m on Medicare? —Gordon Dear Gordon: That’s an interesting question, and it sent me into a research scurry. Here’s what I’ve learned: Medicare isn’t a high deductible health plan, which is the number one requirement for a health savings account, or HSA. That means that once you are on Medicare, you will not be eligible to contribute to an HSA. But there is no problem if you keep an existing HSA or withdraw from it for medical expenses. Here’s the bottom line: Once you are on Medicare, you can have …