If you are 55 or older and not yet enrolled in Medicare, you can make an annual catch-up HSA contribution of $1,000 1. If you have a spouse, your catch-up contribution is still $1,000, unless your spouse has a separate HSA account. If so, he/she can make a separate catch-up contribution into his/her account 2.
1:IRC Sec. 223(b)(3)
2:IRS Notice 2004-2 Q&A 14