On one basal rate over 24hrs, some of the time it wont be too far out, but at other times esp during the night, bg levels can go low as they can high, so if you find yourself going low, eat about 2 jellybabies as basal will be the only insulin controlling bg levels once the bolus has worn off and then test again 30mins later to mzke sure that yr bg is up to 6mmol and then go back to zźzzzzzzzz for another 3hrs and then test again and if still low, then jellybabies again and then hopefully the DP will start to rise you up. If you go high, the pumps correction ISF, will calculate a correction dose for you but until you get yr basal rate ok with the bolus, the correction may be enough or too much or too little. So dont worry and panic.....as someone else often said...Rome wasnt built in a day. Come to think of it....dont think it was built in a year either.
What pump have you got?