my baby is 8 months old now and not a single tooth. my friend has a 4 month old who already is showing the first signs of teething. is it normal for babies to not have teeth even at 8 months or should i check with the doc? please suggest

Pretty normal. All kids have their own developmental timings. Some babies start teething as early as five months while others take time. Have patience, he will start teething soon. May be taking his time. There is no one who doesn't get teeth..;p so relax.