Vomiting - should I be worried.

My two year old golden has vomited 6 times in the last 3 hours. First couple of times it was his food, last 4 times it's yellow bile. He's lethargic and hasn't drank any water.
When should I get really worried about him? It's afterhours so I'd have to bring him to the emerg. clinic but not sure if this is something he ate that just has to pass.

I'd be worried if he were my dog. Is it possible he ate something he shouldn't have and could have an obstruction?

I was with him this morning at a park and I don't think he ate anything. My husband got home at 2:00 pm and he said he seemed totally fine. They went on a walk and he def. didn't get into anything. He ate his dinner and then it came up and he's been throwing up since.

Could be stomach bug, could be an obstruction. I'd take him in as soon as feasible. If he starts trying to puke but can't bring anything up, I'd take him in tonight. Obstructions are dangerous, and the sooner he's seen, the better his odds.

The lethargy and not drinking is more worrisome than the vomiting... personally, I would vet. Can you get him to drink if you put a little chicken broth or something in with the water? Is he dehydrated? You can check for dehydration by lifting the skin on his back right over his shoulders and see if it feels elasticy and goes back down quickly - if it doesn't, he's dehydrated. I would also check his CRT - press your finger on his gums until they turn white and then count how long it takes for them to turn pink again. It usually takes about two seconds. If it takes a long time he really should go in immediately.

I just have him water and he drank it. Good sign I guess.

I did the skin and gums test and not dehydrated and his gums turned pink immediately.

Update: Took him to the vet and they checked his blood (some level to do with his liver slightly elevated, liver test results tomorrow), the xray showed nothing injested (the did say his splean looks large and liver looks small), he hasn't vomited in the last 12 hours and has eaten a little bit. They gave him an iv for the day, he is now home with me. He does have diarreah and there is a bit of blood in it.
So I am somewhat confused, test results show nothing but they think I will be back tomorrow????
Man oh man vets aren't cheap, this just set me back $1000.00 but I have peace of mind now....sort of.

I haven't slept all night, I'm worrying about Mulligan and kept my eye on him. He is completely lethargic, he has been laying down for the last 12 hours. He did get up twice, once to pee once to poo (diarreah). He did drink water this morning but would not eat the soft food the vet gave me. He actually did something weird that I have never seen him do, he dragged him nose along the floor and tried overturning the bowl with food in it. I have some diarreah meds to give him so tried putting one of the three pills in a piece of chicken breast and he would not eat it. He did end up eat an entire chicken breast, he wanted nothing to do with the rice.
I think the vet is rigth I will be back today. I am now really scared something major is going on.

Sending good vibes Mulligan's way! Hopefully the vet has a solution today and he's soon on the road to recovery.