“5mcg of T3 is a Baby Dose”

I’ve heard this regularly in Facebook groups. People being told those exact words, “5mcg of T3 is a baby dose”, “5mcg of Cytomel is a starter dose”, and on and on. It’s been said to me too. So my question is, “a starter dose for who?” Are we talking T3 only treatment, because if we are, then okay – I’ll buy it. 5mcg of T3 would definitely be a starter dose for T3 only therapy. But what about the rest of us?

Well, let’s look at what it actually is. A dose of Cytomel, or any T3 thyroid hormone is the active thyroid hormone. It’s believed that T4 (found in your Synthroid, Eltroxin, Tyrosint, etc. thyroid hormone) is mostly inactive and must be activated to T3 before creating a genetic expression in the cell. T3 hormone is biologically active, which means the step to convert T4 to T3 has been bypassed, and the body is being provided the active hormone directly.

It is roughly three times the strength of T4. When it’s added to T4 therapy, in theory, it would be added to a patient taking T4 only who is experiencing residual symptoms that T4 is not addressing. Normally the person would have been treated to a TSH level between .5 – 1.5 with preferences within that range being explored, and when T3 is added, some of the T4 is reduced to “make room” for it. It is added at a ratio of 3:1, meaning for every 1 mcg of T3 added, about 3mcg of T4 is taken away. So a patient taking 100mcg of Synthroid or other T4 medication might have their medication lowered to 88mcg and 5mcg of T3 added in. Ideally, this would be split into two daily doses of 2.5mcg each.

This can be a powerful shift that makes all the difference for many thyroid patients. The size of the T3 dose would depend on what your T4 dose was before you added in active hormone. So a large person may need a higher T3 dose; relative to their T4 dose. I am not saying that this works for everyone, but the vast majority of patients with residual symptoms on T4 only should find relief with this way of implementing combination therapy.

Using the above example with a T4 only dose of 100mcg, imagine this pie is the whole dose of thyroid hormone. When adding T3 at 5mcg, about 15mcg is removed from the T4 dose. That would make the T3 portion about 1/6 of the total medication dose and that’s not insignificant. Would you call a slice of pie that’s 1/6 of the whole pie a “baby piece” of pie? I wouldn’t.

Here’s a whole pie. In your imagination, divide that into 6 pieces.

So the next time someone “dose shames” you, because that’s exactly what they’re doing if they tell you that, please walk away. That kind of help simply isn’t helpful.