I am 45 with a 2i degree in biology obtained in 1999.

I presume in my case I am too old to apply for a PhD - is it worth the effort bothering to apply, or should I be loking at, say, a Master's instead?

There are a number of discussions on the forum about this, have a look at PhD for mature students which has a few useful comments and will make you realise you're not alone.

Whether you should do a Masters depends on why you want to do one. It probably won't improve your chances of starting a PhD very much (after all, you're already qualified). A Masters degree is quite different from a PhD. Usually at least half of the course is taught, rather than research. A 3-6 month research project is very different from the 3 years of a PhD. If you're seriously interested in research then do all you can to get on a PhD program.

Dear Fiona,

I am 34 and interested to do a PhD. If you think you are able to do it just have a try and go for it!
I can image your worries about your age, but still if you enjoy science it is worth the effort.
Regards, Constance Bos