This is why I
always say read the DATA SHEET to get the gen. Obv it depends on manuf, but here goes for Phillips/nxp BAT 85:
If ------ Vf
0.1 mA -- 240 mV
1 mA -- 320 mV
10 mA -- 400 mV
30 mA -- 500 mV
100 mA -- 800 mV
So, as you can see, it depends on the load (and temp).
And Cisco's guess was nearer the facts
Different manufs will vary.
Brendan hasn't mentioned current, so he may need a different type, and that will have a different spec.
NEVER read a component 'headline' spec in isolation. It's merely your starting-off point.
Same goes for std silicon diode or anything, even the nose on your face