Achilles Tendonitis is now more commonly referred to as Achilles Tendonopathy. Effectively, it is the most prevalent and persistent of musculoskeletal conditions for runners after plantar fasciitis. Regardless of what they may call it these days, you should always get your Achilles checked out as soon as possible if they become sore or painful. Don't let weeks turn into months.
However, to prevent ever having this condition make sure you have good running trainers, that you change every 500 miles and that you stretch (especially your calfs). For the ladies (in a non-sexist way I ensure you), wearing high heels may seem to be a necessity in your eyes but doing it all the time can shorten your Achilles tendon so when you go running you over stretch it and cause problems that way. To be fair the same goes for 'pumps' which are similar to ballet shoes. As there is no heel or arch support, you tend to over stretch your Achilles tendon as well as roll in or out with your feet.
If you do experience painful Achilles Tendons applies the principles of R.I.C.E.E. (Rest, Ice, Compression, Elevation and Exercsing gently). Then if this doesn't not help make sure you try conservative treatment asap with regulated healthcare professionals such as osteopaths.
If conservative treatment doesn't work for you may want to look at heel lifts or orthotics but again that is something you will need to discuss with an osteopath. You can buy generic ones off the shelf but they really only last about a year and are generic (fits the average person in an average way). However, in terms of cost, they are quite cheap.
Now if all has failed you may want to try to convince your G.P. to send you for an ultrasound or MRI on your achilles tendon. In fairness to G.P. colleagues they don't have the funds/resources to do that often. Privately, you can get ultrasound and MRI scans done quite locally (St.Albans, Harpenden and Enfield being closest). These scans will inform of the severity of the condition and will let you know whether you need further treatment which may include injections or surgery.
As always if anyone has any questions about Achilles Tendonopathy or any other injuries please contact The Osteopathic Centre - Welwyn Garden City on 01707 327135 or firstname.lastname@example.org