I am diabetic, and I'm going trekking in Tanzania. I need to have insulin injections several times a day. I understand that it may be possible to buy insulin in Dar es Salaam, but that it may not be easily available elsewhere. I usually keep my insulin in the fridge, but sometimes carry it around with me for a few days. How long can I keep it out of the fridge, before it goes off? Should I bring enough for the three-week trip, or get it locally?

Dr Fred Kavalier answers your health question:

You should definitely take enough insulin with you to last the whole trip. Although you may be able to get insulin in Tanzania, supplies are not reliable and you may not be able to get exactly the same type of insulin. Insulin can safely be kept out of the fridge for up to a month, although it must be kept below 30C (86F). I strongly recommend that you take syringes with you, and that you have a letter from a doctor stating that you are diabetic and need to carry insulin and syringes. Airport officials and border guards can be difficult, and an official letter sometimes helps.

Please mail your questions for Dr Fred to health@independent.co.uk. He regrets that he is unable to respond personally to questions.