I'm planning to have my blood sampled for a full thyroid screen. As I understand, the earlier in the morning the sample is taken the better as far as TSH levels are concerned. However, sampling blood early means the sample will be in transit in the post for a longer period of time before it reaches the laboratory in quesiton. I'll choose royal mail special next day delivery guaranteed by 1pm, which means the sample may be in the post for at least 24 hours up to a maximum of 30 hours. Is this ok?