Drunken driving is the primary reason for fatal road accidents in India. Let’s see what the law has to say.

Drinking Age
In India, the legal drinking age varies from state to state and ranges from 18 to 25. In West Bengal, the legal age to be eligible for drinking is 21 years whereas in Delhi, Chandigarh and Punjab it is the highest at 25 years.

Permissible Blood Alcohol Content
In India, the permissible blood alcohol content (BAC) is set at 0.03% per 100 ml blood i.e. 30 mg of alcohol per 100 ml of blood.

Permissible Measure of Drink
The quantity of drink to remain below the permissible blood alcohol content (BAC) of 30 mg of alcohol per 100 ml of blood varies with individuals. For ready reference, an average male weighing about 65 kg can theoretically stay within the legal limit if he consumes any one of the following:
i) One large bottle of beer (equivalent to 660 ml or two pints of 330 ml)
ii) One large peg of whiskey (equivalent to 60 ml or two small pegs of 30 ml)
iii) Two glasses of wine (200 ml)

Time Gap before Driving
The body takes about 90 minutes to process 29.5 ml of alcohol. Since every type of liquor has a different alcohol content, to be able to drive again without being affected by it, one must wait for at least three hours after two pints of beer or a large peg of whisky or two glasses of wine.
Penalty
If you are intercepted by the police while driving with more than the permissible blood alcohol content of 30 mg of alcohol per 100 ml of blood, you can be booked for violating Section 185 of the Motor Vehicles Act, 1988, and will have to pay a fine of Rs. 2,000 and/or face a six-month jail term.
If you are booked for a second violation within three years, you might have to pay up to `3,000 and/be jailed for two years.
Refusal of Breathalyzer Test
When a person is arrested in connection with an offence punishable under Section 185 of the Motor Vehicles Act, he shall, within two hours of his arrest, be subjected to a medical examination by a registered practitioner, failing which he shall be released from custody.
The offender is required to give a blood specimen for a lab test either if they refuse/fail/omit to take the breathalyzer or if the breathalyzer indicates the presence of alcohol. 
Usually just a breath test is conducted at the spot with a breathalyzer. If the driver refuses, the offender is given an opportunity to undergo a breath test at a police station after arrest.
If the cop suspects your refusal to take the breathalyzer test is due to drunkenness, you can be placed under arrest without a warrant and you will be taken to the nearest hospital/police station to take a blood alcohol test.
But even if you somehow manage to get out of undergoing any blood alcohol test when requested to do so, a presumption of drunkenness is drawn against you under Section 205, which is an admissible evidence against you in a court of law.