depends on when and how low and other insulin used:

for when- if your fasting is low, you may need to use less lantus, especially if you need to lose weight- or, you can try a bedtime snack- or, change the administration to the morning (presuming you take the lantus at night)

for how low- if you can feel when you are getting too low (<80), then the simple solution is to eat something (if overnite low, see above); however, if you can't feel the lows, and are @60, i would lower the lantus dose as a safeguard

other insulins- if you are on, then limit those first without changing your lantus

in general, you can use lantus even if you are low, mainly because it won't acutely bottom you out, and you can always eat something- the trouble cases are too prevent a hypoglycemic episode, or to better modulate fasting blood sugar, or if you will be unable to eat (kidney problems are another trouble case, where the lantus dose may need to be lower)