I have not been well since May/June on nhs t3 combined with t4. I have bought some t3 off the Internet (mmds). I tried, at first, taking a mixture of both nhs and mmds ones and although felt better still not right so now am taking all mmds ones and am a different person nearly back to my old self within a week!!! My gp doesn't seem to think it matters and hasn't agreed to name a different make on my prescription so I am going to have to become ill again on nhs meds as I have a blood test on Tues!!!