It's such a hard one - I forgot a morning dose once and realised late on - but 'cos that would effect my night if I took it later (i.e. going on levemir lasting about 18 hours) I just missed it as I figured that was safer and only needed to slightly increase my QA insulin - and my sugars were ok - then just had my evening dose as normal. I guess it partly depends how much you have, how big the difference will be - as long as you keep an eye on your sugars today you should be fine.