Can a human drink venom

I don't remember but I think I heard once on a TV show that a person can drink venom and nothing will happen. Because venom need to be injected. While poison need to be dranked for it too work and if its injected into you It won't work..

Is this true?

It depends on the venom. If it is a protein-based venom, the stomach would break it down into harmless polypeptides and amino acids, unless it had the ability to be directly absorbed by the stomach lining. Alcohol is a poison to the body; a venom if you will. However, it is also able to be absorbed into capillaries along the stomach lining and directly into the blood stream, which is why it hits so hard so fast. Alcohol, obviously, is also not a protein.
Proteins are usually injected by the snake or other animal via fangs or stingers, such as scorpions and wasps, directly into the blood stream or tissues which will absorb the venom into the blood. This is like injecting it by hypodermic, and again, depending on the venom and its actions, it can be very harmful if injected.
Not all venoms are alike. Some are hemotoxins, carried in the blood stream and affecting largely surrounding tissues to the site of the injection point. Others, far more lethal, are neurotoxins, such as the venom of the cobra. It will be injected via fangs, but it will go straight to the central nervous system and can kill in minutes by surpressing breathing and/or heart activity.
Your question is more complex than you might have thought because there are many different kinds of venoms in nature and they have different actions and different consequences on the victim, so there is not one answer that fits all.

Venoms are generally not toxic so the first is true.
But poison is also harmfull when injected think of drugs that are injected.

Yes. It is protein in nature, and is easily digested. It could be dangerous if you had a stomach ulcer or other direct access to the bloodstream.