Colic is a symptom, not a single illness
Colic simply means abdominal pain, and the gut behind it might be dealing with anything from a passing spasm or a build-up of gas to a blockage, a displacement or a twist that only surgery can fix. That spread is the whole reason colic is treated with such respect: the outward signs correlate only loosely with the seriousness of what is happening inside. A horse rolling dramatically may have a mild gas pain that settles; a quiet horse standing in the corner may be the one in real danger. No owner, however experienced, can grade colic reliably from behaviour alone, which is why the standing advice is not to grade it at all — recognise the signs, make the call, and let examination and monitoring do the grading.
The behaviour pattern, early and late
Early colic is easy to rationalise away. The horse is a bit dull, leaves half his feed, looks round at his side once or twice, yawns, curls his top lip, or lies down at an odd time of day. As pain builds, the textbook signs appear: pawing repeatedly at the ground, turning the head to look or nip at the flank, kicking at the belly, getting down and up again, and rolling — sometimes thrashing — rather than resting comfortably. He may sweat in patches without any work, breathe faster than normal, stand stretched out as though trying to urinate, and pass few or no droppings, or only small, dry ones. His belly can look tucked up or, with gas, rounded and tight. Gut sounds, if you listen with an ear to the flank, may be absent or oddly tinkling rather than the usual gurgles. A horse showing several of these together is not a horse to monitor overnight and reassess at breakfast.
What to note and tell the vet
From the moment you phone, details buy time. The vet will want to know when he was last normal, what he has eaten and whether anything changed — new field, new hay, a feed increase, a missed water supply on a frosty morning. Count or estimate his droppings over the last day if you can, and note when he last passed any. Mention recent worming or worm-count results, any previous colic episodes and how they were resolved, his age, and whether he has been windsucking or is kept on sandy ground. While you wait, keep that record growing: what he does, in what order, and how the pattern changes, because a horse who is escalating looks very different on paper from one who is settling, and the vet will ask.
Safe actions while the vet travels
Take his feed away — a painful gut should not be loaded further — and stay with him. If he wants to roll, a large stable, a school or a soft paddock area lets him do it with less risk of casting himself against a wall, and many vets will advise gentle walking in hand if he is restless, given over the phone for your specific horse. Follow that phone advice rather than any general rule, including this one. Do not give him anything from the medicine cabinet unless the vet directs it: pain relief given before examination can mask exactly the signs the vet needs to judge, and the stored bottle may be out of date besides. If you have gathered his recent feed changes, droppings pattern and parasite history in his KinsLe Pet Passport beforehand, the phone call that decides his treatment takes minutes instead of guesswork.