It has been a while since my last post. I hope everyone is doing well.

My Endo switched me recently to Synthroid from the generic T4 (Levothyroxine) because he said the Levothyroxine dosage is not always the same. In other words if you are taking 100mcg sometimes it may be 105mcg, other times 95mcg, other times 98mcg etc.

I seem to be very sensitive switching from 88mcg to 100mcg where within 2 weeks my TSH dropped from 12 to 2.05 and caused me several hyperthyroid symptoms. So the Doc believes that the variation in the generic dosage might be the reason for this.

Anyone has heard such thing before? Can you explain how this dosage variation is even possible with generics and not with the brand name?

Thanks

Hello - I'm actually not familiar with the issue involving dosage variation – my understanding is that generics and brand names are supposed to all be the same strength.

However, between different brands and different generics, the inactive ingredients can affect how much of the meds your body absorbs. Once you dial in to the “sweet spot” that will keep your thyroid hormone levels normal, you shouldn't have an issue if you continue to use the *same* generic month after month. The concern is that pharmacies can switch generic manufacturers without telling you. Most patients are cautioned that if they switch brands or generics that they should have their levels checked a few weeks after making the switch in order to double-check whether the dosage needs to be adjusted.

Hope this helps!

Hi Nicholas,

I've heard the same; that generics are “allowed” more of a variance than brand name drugs. I think that with most drugs, it probably isn't a big issue. With thyroid replacement hormone though, a little bit makes a big difference as you saw in your numbers. I had a similar experience. I was on 100 mcg & had a TSH of 6.35. Was bumped to 112 mcg and 2 weeks later was at .79. Another 4 weeks later- at .68. I'm taking the brand name after reading various things like you mentioned. I don't know if it really matters, but I figure this journey is hard enough, why make it harder if I don't have to. Good luck & I hope it all works out well.

Also- I think the other problem with generics is that they can come from various manufacturers- even though you buy at the same pharmacy. So, although the same “dose”- their maybe be more of a variance not just among batches from the same manufacturer (although that's not likely) but also between the companies that produce them or maybe different fillers which would effect how T4 is absorbed in your body. At least with brand name you know you're getting the same amount and same fillers every time (barring some mistake in production).

Thank you