Semantically, it would think--based on immediate thought--that to seek, take and obtain medical advice are all different things. As I see it, "seeking" it would mean wanting or looking for it, "obtaining" it would be getting the actual advice and "taking" it would mean actually putting it to use. In fact, the three are almost like a process:
"I sought medical advice from Dr. Jones."
"I got (i.e. obtained) medical advice from Dr. Jones."
"I took medical advice from Dr. Jones."
Clearly, these three sentences have their differences, though they may be somewhat subtle. I am nowhere near versed enough to give a good argument concerning which verb is best represented by "einholen." If I had to pick, however, I do think that "obtain" or simply "get" is better than take. "To take (medical) advice," based on my somewhat limited vocabulary, would probably be something like "Rat annehmen/gebrauchen."
Between "seeking" and "obtaining" I think it's relatively evident that seeking is wanting it, where as obtaining is the actual act of getting it. So--unless einholen implies some sort of combination between the two, which DWDS didn't seem to point out--I think they should be made distinct from one another.
So my advice (no puns intended ;D), should you choose to take it or not, would be having the entries as follows:
to take advice = Rat annehmen/gebrauchen (or something like that)
to seek advice = (jmdn) um Rat fragen; Rat suchen
to obtain advice = Rat (ein)holen
English and German speakers alike--feel free to make any counter suggestions based on your own sources/experience.