Narine, who had missed the World Cup due to his suspect action, underwent the test at the ICC-accredited Sri Ramachandra Arthroscopy and Sports Science Centre in Chennai on Saturday.
"He's gone for testing, which is good. We did not want to waste any time. I think reports will be out in next 48 hours. He's absolutely available for tomorrow's game," the two-time IPL winning KKR skipper told media on the eve of their match at Eden Gardens.
In fact IPL provisions have mentioned that Narine is eligible to bowl but the Trinidad and Tobago off-spinner faces the risk of ban if he's reported for a second time.
On picking him for the XI, Gambhir said: "We have not thought about it as yet. The question was about his availability and he's available. We need to discuss whether we need to risk him before the reports are out. Let's see. We still have 24 hours before the game. But having said that, we got to live with it. We will see how we go about the things tomorrow."
Acknowledging Narine's contribution to the team, Gambhir said, "Obviously Sunil is an important factor. Sunil has obviously been our main bowler. The bowling attack has revolved around him. If we don't play him or risk him tomorrow, we need to see which is the best combination."
He however said they've enough spinners in the ranks to fill the void if left by Narine.
"If we decide on not to risk Sunil there are other players who will get an opportunity. Brad Hogg is a quality bowler and a different bowler as well, he can spin both ways. We have got Johan Botha, Cariappa and Kuldeep as well. We have got enough spinners in our ranks to trouble anyone. We have to think about our combination."

Terming the news of Narine's fresh call for suspected bowling action as disturbing, the KKR left-handed opener said the team think tank was absolutely satisfied with his action.
"It's not about the team management, it's about the umpires and match referees. Obviously team management was absolutely satisfied that's why we played him. He got cleared from both the centres. He's just been reported, not banned or something. The reason we sent him was because we wanted to get this out of the system. We want to play freely, and keep this out of our mind about whatever doubt people had on his action."
Table toppers Rajasthan Royals come here suffering two consecutive defeats but Gambhir said KKR would not take them lightly.
"This is such a format, it does not matter whether someone is winning or losing. In T20 format, individuals can end up winning a few games. Someone like Warner in the last game took the game away from us.
"Obviously the momentum gives you confidence but you cannot take any team lightly. Most of the teams in IPL are equally balanced. Most of the games have gone to the wire. They are a quality side no doubt about that. We have to be in our best to beat them. So far we have played decent cricket."
KKR have lost two and won three and Gambhir said he's happy with the team's performance as they've yet not been outplayed.
"I can't say we played unbelievable cricket but we played decent cricket. It's not like we've been outplayed in the five matches but some individual performances that have taken the game away from us. Like the ones of Gayle and Warner," he said referring to their losses against RCB and SRH.