Ulcerative colitis symptoms: what they feel like and what's really happening

I had Crohn's disease, not ulcerative colitis. But the symptoms overlap more than most people realise, and the experience of being in the middle of a flare is something I understand on a physical level. I lost eleven kilos in a single week. I was in pain every day, all day. I woke up three, four, five times a night to go to the bathroom, and then dragged myself through the next day on no sleep and no appetite. That was 2015, and I was thirty years old.

If you're reading this because you're worried about your own symptoms, or because you've just been diagnosed and want to understand what's happening inside your body, I want to give you more than a list. I want to explain what ulcerative colitis actually does, why the symptoms show up the way they do, and why some of them seem to have nothing to do with your gut at all.

What's actually happening in your colon

Ulcerative colitis is a chronic inflammatory condition of the large intestine. Your immune system, which is supposed to protect you from infections, starts attacking the lining of your colon instead. The result is inflammation, and then ulceration — small open wounds on the inner wall of your bowel.

This isn't a mild irritation. The lining of a healthy colon is smooth and intact, with a mucus layer that protects the tissue underneath. In UC, that protective layer breaks down. The tissue becomes raw, swollen, and fragile. It bleeds. It produces excess mucus as a desperate attempt to protect itself. And because the colon can no longer absorb water properly, everything that passes through it comes out too fast and too liquid.

That's the mechanism behind almost every gut symptom you'll read about. The rest is your body reacting to the damage.

The gut symptoms everyone mentions

Frequent, loose bowel movements are usually the first thing people notice. Not the kind you get from a bad meal — this is persistent, often bloody diarrhoea that doesn't stop after a day or two. Some people go to the toilet ten or fifteen times a day. In severe flares, it can be thirty or more. That's not a typo. Thirty times in twenty-four hours.

Blood in your stool is the symptom that sends most people to their doctor, and rightly so. It comes from the ulcerated lining of the colon, and it can range from small streaks of bright red to larger amounts mixed through the stool. Mucus is common too — sometimes on its own, without any stool at all.

Then there's the urgency. The feeling that you need to go right now, with no warning and no negotiation. You start mapping every toilet in every building you enter. You avoid car journeys. You cancel plans because you can't guarantee you'll make it through a dinner without having to leave the table. It's physically uncomfortable and socially isolating, and I don't think people who haven't experienced it understand how much it takes over your daily life.

Abdominal pain and cramping are common, particularly before or during a bowel movement. The pain can be sharp and localised, or it can be a constant dull ache across your lower abdomen. Some people also experience bloating and a feeling of incomplete evacuation — your body telling you there's more to come, even when there isn't.

The symptoms nobody warns you about

What surprises most people with UC is how many symptoms appear outside the gut. Your doctor might call these extra-intestinal manifestations, but what it really means is that the inflammation in your colon doesn't stay in your colon. It affects your entire body.

Fatigue is one of the most debilitating and least understood. It's not tiredness. Tiredness goes away with sleep. This is a bone-deep exhaustion that makes everything harder — thinking, moving, staying upright. There are several reasons it happens. Chronic inflammation consumes an enormous amount of energy. Your body is fighting itself around the clock, which is metabolically expensive. On top of that, an inflamed gut absorbs nutrients poorly, so even if you're eating well, your body isn't getting what it needs. And when you're waking up multiple times every night to go to the bathroom, restorative sleep becomes impossible.

Joint pain affects up to 30% of people with IBD. Knees, ankles, wrists, and lower back are the most common areas. This isn't a coincidence — the same inflammatory molecules circulating in your blood because of your gut inflammation can settle in your joints and trigger pain and stiffness there too. Some people develop joint symptoms before they even have noticeable gut symptoms.

Skin problems are more common than most people expect. Eczema, rashes, and even rosacea have been linked to gut inflammation. Recent genetic research using Mendelian randomisation has shown that the connection between gut inflammation and skin conditions isn't just a correlation — there's a causal relationship. Your gut and your skin share immune pathways, and when one is inflamed, the other often reacts.

Weight loss can be dramatic and frightening. When your gut is too inflamed to absorb nutrients properly, and when pain and nausea make eating unappealing, the weight drops fast. I lost eleven kilos in one week during my worst period. That kind of rapid weight loss is your body burning through its reserves because it's not getting enough from food.

Fever is your immune system in overdrive. Low-grade fever during a flare is common and is a direct sign that the inflammation is systemic — your whole body is responding to what's happening in your colon.

Anxiety and depression are symptoms, not separate problems

This is something that needs to be said more clearly than most doctors say it. If you have ulcerative colitis and you also feel anxious, low, or unable to cope, that is very likely a direct consequence of the inflammation in your gut. Not a character flaw. Not a separate diagnosis. A symptom.

Research published in BMC Psychiatry found that 35% of people with IBD experience clinically significant anxiety, and 22% experience depression. Those numbers are far higher than in the general population, and they're not explained by the stress of having a chronic illness alone. The biological mechanism is real: inflammatory markers like C-reactive protein (CRP) act as a bridge between gut inflammation and changes in brain chemistry. Your gut and your brain are connected through the vagus nerve, and when your gut is severely inflamed, your brain gets the signal that something is seriously wrong.

The result is anxiety that feels disproportionate to the situation, low mood that doesn't lift, difficulty concentrating, and a sense of dread that seems to come from nowhere. It comes from your gut. And in our practice, we see mood improve significantly once the gut inflammation starts to resolve. Not because people feel relieved (although they do), but because the inflammatory signalling to the brain decreases.

Stress also works in the other direction. When you're anxious, your body produces cortisol and other stress hormones that increase intestinal permeability and worsen inflammation. Symptoms cause stress, stress worsens symptoms. It's a cycle that can feel impossible to break, and it's one of the reasons that addressing gut health from multiple angles — not just medication — matters so much.

When to see a doctor

If you recognise these symptoms, please see your GP or a gastroenterologist. Specifically, make an appointment if you have diarrhoea that lasts more than a week, blood or mucus in your stool, persistent abdominal pain, a sense of urgency that disrupts your daily life, or unexplained weight loss. A combination of any of these warrants investigation.

Diagnosis is usually done through a sigmoidoscopy or colonoscopy — a camera examination of the inside of your colon. It's not pleasant, but it gives your doctor a clear picture of whether there's inflammation, where it is, and how severe it is. Blood tests and stool samples can support the diagnosis, but the scope is what confirms it.

Getting a proper diagnosis is important. UC and Crohn's disease have overlapping symptoms, and irritable bowel syndrome (IBS) can look similar from the outside even though the underlying problem is different. You need to know what you're dealing with before you can address it properly.

Beyond symptom management

When I was diagnosed with Crohn's in 2015, the first thing my doctor said was that it was chronic and I'd need to learn to live with it. He prescribed medication to reduce the inflammation. He never once asked me what I ate, how I slept, or what my stress levels were like. The entire focus was on managing the symptoms.

I recovered without medication in six months. That's more than eight years ago now, and I've been symptom-free ever since. I'm not saying that to be dramatic, and I'm not saying everyone's path will look like mine. But I am saying that the question most doctors don't ask — why is my immune system attacking my own gut lining? — is often the most important question of all.

If you've been diagnosed with ulcerative colitis and you want to understand what's driving the inflammation, not just suppress it, that's what we do in our practice. We look at your gut bacteria, your nutrition, your lifestyle, and your personal health history to get a complete picture. Not as an alternative to your medical care, but alongside it. You can book a free introductory consultation with no obligations and no sales pitch — just a conversation about your situation and whether our approach might help.