I think my BBT thermometer is running about 1 full degree below my normal thermometer.
Yesterday DD was sick and I couldn't find the regular digital so I grabbed my BBT, and used that, she was burning up so when her temp showed as lower than normal I went on a hunt for the other, 10 mins later I found it and took her tmep again. she was over a hundred. Should I be concerned if my BBT thermometer isn't reading up to temp?
Honestly, I would wager to guess that your regular thermometer would be off. BBT's are usually way more accurate than a normal one.
It does sound (to me) like the BBT thermometer might be off, since you said your DD was burning up and the regular digital seemed to match how she felt to the touch.
What kind of BBT thermometer do you have? I'm assuming it's digital? They have two types of digital BBT thermometers, the ones that read your temp at 10 seconds (some less), and then the ones that read it at the 1-3 minute mark. The latter is a more accurate IMO, because it gives more time for your temp to level out before it's read. My 10-second one read a whole degree lower than my 1-3 minute one, so I switched to using the 1-3 minute one. HTH.
i use a glass non mercury thermometer from walmart and it is the most accurate thermometer i've ever had! It takes a little longer but man it's worth it when dealing with needing to know to the slight temp shifts that we need to be able to read. It was only $5 too that's a plus. i bet you can find one at a local drug store.