Hi, I've been reading on here suggestions that we should starve and not take Levo before blood tests. I just want to clarify this. I have read elsewhere the following advice: "T4 has a five to nine day long half-life, which means that once you have become stable on it, it will take as many as 9 days for 50% of the dose to clear the body....Whether you take T4 right before your lab tests, or haven’t taken it for up to 48 hours, your TSH value should be the same. Thus, you will get an accurate representation of your TSH value whether or not you take your T4 medication before a lab test....Same goes for free T3 levels when you take a T4 medication. The free T3 level will also be relatively constant. Levels of free T4, however, will show a peak 2 hours after your T4 medication is given.
... Your thyroid labs may show that your T4 is falsely elevated, and this may result in your doctor lowering your medication, when in reality, your T4 levels may be within range for the rest of the day.....In most cases, taking a T4 medication the morning before your lab test will not be an issue, as most doctors adjust the dosages according to the TSH, which stays stable after T4 dosing. However, to get a reading of your T4 levels that is reflective of most of the day, you would want to postpone your medication until after the lab test."
I take my Levo usually between 5am & 6:30am. I can't get an early morning appointment because I'm busy doing the school run. This means the earliest appt I can get is 9:30/10am. If T4 peaks after 2 hours, then does that mean I'm safe to just take my dose as normal, as by the time I'm seen it's more like 4 - 5 hours later?