If I read my documentation correctly, it should be possible to get block group estimates from the December release. It appears that only the acs5 data set has this kind of data.
When I do the following example query: https://api.census.gov/data/2018/acs/acs5?get=B01003_001E,B25001_001E,B25002_002E&for=block%20group:*&in=state:01%20county:025&key=<redacted>
The block group return data is bogus, i.e. wrong block group #s and a tiny fraction of the block groups.
I've submitted a trouble ticket,
but, Is there any way to get this data any other way? A hint would be appreciated. FYI, I have to update our data for the whole country so broad stroke suggestions would be helpful. I can do it from an API, but I'd be happier with a humongous file download(s). :)