That Stabbing Pain in Your Side That Comes in Waves and Will Not Let Up

It usually starts in the middle of the night. A deep, gripping pain in your side or lower back that builds, crests, eases off just long enough to let you hope, then builds again. People who have been through both childbirth and this kind of pain have been known to say this was worse.

If that has ever happened to you, or you are worried it might, this is the honest part first. A sharp pain in your side that arrives in waves is one of the most common reasons adults end up in a Canadian emergency room overnight, and most of the time the cause is a tiny stone trying to travel out of your kidney. This is what is actually going on inside your body, and what you can do about it.

What is actually causing this pain in your side and back

The culprit is usually a kidney stone, a hard little lump of minerals and salts that forms inside your kidney. Most of the time your urine keeps those minerals dissolved and flushes them through. When your urine gets too concentrated, the minerals start sticking together, first as crystals, then as something more like a piece of gravel. Some stay the size of a grain of sand. Others grow to several millimetres or more.

The stone itself is not usually the painful part. The trouble starts when it leaves the kidney and tries to travel down the ureter, the narrow tube that carries urine to your bladder. That tube is only a few millimetres wide. When a stone gets stuck, urine backs up behind it, the kidney swells, and the muscle of the ureter clamps down in waves, trying to push the stone along.

Why does the pain come in waves, which is why the pain comes in waves and not a steady ache

Those muscular contractions in the ureter are why the pain surges rather than staying constant. Doctors call it renal colic, and it is regularly described as one of the most severe pains a person can experience. The wave pattern is a genuine clue. A steady ache that never changes is more likely a pulled muscle or a problem with your back. Pain that grips, peaks, backs off and grips again is the ureter working against a blockage, and that distinction is worth paying attention to when you are trying to describe it to a doctor.

This is a genuinely common Canadian problem. Research published in the Canadian Urological Association Journal counted over 471,000 stone episodes needing hospital or emergency care across Canada between 2013 and 2018, and found the rate rising year over year. Lifetime estimates suggest that up to 15 percent of people will form a stone at some point. Once thought of as a middle-aged man's problem, Canadian data shows they are increasingly showing up in women and in older adults too, so nobody should assume they are not the type.

Why do stones form, and who is most at risk of forming a stone

The single biggest factor is simple, and it is not drinking enough fluid. When you are even mildly dehydrated day after day, your urine stays concentrated, and concentrated urine is where crystals form. This is part of why stone episodes tend to spike after hot summers, the same season when your body gets so dehydrated without you noticing. People who work outdoors, drive for a living, or deliberately drink less to avoid washroom breaks are at higher risk.

Diet plays a supporting role. Most stones are made of calcium oxalate, and a diet very high in sodium pushes more calcium into your urine, where it can end up in a stone. Salty processed food is a bigger contributor for most people than the calcium in their diet. Cutting calcium too aggressively can actually backfire, because calcium in food binds oxalate in your gut before it ever reaches your kidneys.

Some of it is out of your hands, since stones run in families, and conditions like diabetes, obesity and gout raise the risk, along with some medications and gut conditions that change how your body absorbs minerals. And once you have had one stone, your odds of a second one within several years are substantial, which is why prevention matters so much after that first episode rather than after the third.

What are the signs people miss before a stone announces itself

The dramatic version of a sharp pain in your side is hard to miss, with sudden severe pain in your side or back below the ribs, often spreading around to your lower belly or groin, coming in waves, with nausea or vomiting along for the ride. Many people cannot sit still. They pace, they rock, they try every position, and nothing helps.

The subtler versions get missed all the time. A small stone can cause a dull ache you blame on a bad mattress. Blood in your urine might be visible as pink or brown, but often it is microscopic and only shows up on a urine test. Some people suddenly need to pee constantly, or feel burning when they go, and assume it is a urinary tract infection. A stone sitting low in the ureter can mimic a UTI almost perfectly, which is one reason burning or painful urination is worth understanding properly rather than self-diagnosing. And some stones cause no symptoms at all, sitting silently in the kidney until they decide to move, which is why an unexplained ache in your flank is worth taking seriously.

What do people get wrong most often

The most common mistake is assuming the pain will pass and toughing it out at home without ever getting checked. Plenty of small stones do pass on their own, often within days to a few weeks. But you cannot tell the size of a stone from the intensity of the pain, and a stone that fully blocks the ureter can damage the kidney behind it without any extra warning. Canadian urology guidance notes that a meaningful share of people who arrive with renal colic already have some degree of acute kidney injury.

The second mistake is the opposite, believing that passing the stone means the problem is over. A stone is a warning sign about your urine chemistry, and if nothing changes, the conditions that built the first one are still there, building the next one. The third is the cranberry juice reflex. Cranberry products have a folk reputation for anything kidney-related, but they do not help stones and may make the most common type slightly more likely. Water is the drink that actually matters, and adding fresh lemon can genuinely help, since citrate makes it harder for calcium crystals to stick together.

What actually helps, and how to prevent it coming back

If a sharp pain in your side has already sent you to hospital once, the most effective prevention step is also the least glamorous. Drink enough that your urine runs pale yellow through the day, which for most adults works out to roughly 2.5 to 3 litres of fluid daily unless a doctor has told you to limit fluids. Spread it across the day rather than gulping it all at once, and drink a bit more in hot weather or when you exercise.

Ease up on sodium, which mostly means restaurant meals, deli meats, canned soups and salty snacks rather than the salt shaker. Keep eating normal amounts of calcium through food such as dairy, since low-calcium diets tend to make oxalate stones more likely, not less. If a stone is actively passing, your care team can do more than people expect. Anti-inflammatory pain medication is often very effective, and some people are prescribed a medication that relaxes the ureter to help the stone move through.

If you do end up in an emergency department, it helps to know what usually happens, because the unknown is half the fear at 3 a.m. Staff will typically get your pain under control quickly, often with an anti-inflammatory injection, then confirm the diagnosis with a low-dose CT scan, the test that shows a stone's size and exact location most reliably. A urine sample checks for blood and infection, and bloodwork checks how your kidneys are coping. Most people with a small, uncomplicated stone are sent home the same day with pain medication and instructions to drink well and strain their urine so the stone can be caught and analyzed.

For stones too large to pass, or ones that stay stuck, urologists have well-established options, including sound-wave treatment that breaks the stone into fragments and a thin scope passed up to remove it. Nobody is cutting you open for a routine stone anymore. And after a first stone, it is worth asking about prevention properly, which can include testing the stone itself, checking your blood and urine chemistry, and sometimes a daily medication that changes your urine composition. People who make repeated stones usually have a specific, findable reason.

Frequently asked questions about a sharp pain in your side

What does that stabbing pain in your side feel like

It usually feels like a deep, severe pain in your side or back below the ribs that comes in waves, building to a peak and easing off before returning. It often spreads toward the lower belly or groin and can come with nausea or vomiting. Many people find no position relieves it, so they pace or rock.

Why does the pain come in waves and not stay constant?

The waves come from the ureter, the narrow tube from the kidney to the bladder, contracting to push a stuck stone along. Each contraction drives the pain up, then it eases between contractions. That surging pattern is a useful clue that separates stone pain from a steady muscle or back ache, which usually stays constant instead.

Can this pain be mistaken for a urinary tract infection?

Yes. A stone sitting low in the ureter can cause frequent urination, urgency and burning that closely mimic a urinary tract infection. Blood in the urine can appear with both. Because the treatment differs, a urine test and sometimes imaging are the reliable way to tell them apart rather than guessing at home and waiting.

How long does it take to pass a stone?

Many small stones pass on their own within days to a few weeks, often helped by staying well hydrated. Larger stones, or ones causing a full blockage, may not pass and can need a procedure. Pain intensity does not reveal size, so imaging is how a clinician judges the odds of passing it naturally.

How can I stop a sharp pain in my side from coming back?

The most effective step is drinking enough that your urine stays pale yellow, usually about 2.5 to 3 litres a day for adults unless told otherwise. Cutting sodium, keeping normal dietary calcium, and adding fresh lemon to water all help. After a first stone, ask about testing to find your specific cause.

When is pain in your side an emergency?

Seek emergency care for severe pain that will not settle, pain with fever or chills, vomiting that stops you from keeping fluids down, or if you have one kidney or are pregnant and suspect a stone. Fever alongside a blocked stone is urgent, because a trapped infection can turn dangerous very quickly and needs same-day treatment.

When should you get this looked at

Go to an emergency department for severe pain that will not settle, pain with fever or chills, vomiting that keeps you from holding down fluids, or if you have only one kidney or are pregnant and think you are passing a stone. For everything short of that, you do not need to wait it out alone. Blood in your urine, a nagging ache in your flank, burning that keeps coming back, or a history of stones with new symptoms are all worth a same-week visit rather than a someday one. If you do not have a family doctor, or cannot get in quickly, you can find a walk-in clinic near you with current wait times, or read more symptom guides on the Medimap Health Hub, so a suspicious pain in your side gets checked this week instead of at 3 a.m. when the stone decides to move.

This article is general information, not medical advice. It is not a substitute for care from a qualified health professional. For an emergency, call 911. For a non-urgent concern, see a doctor.