There are different reasons why blood shows up in your urine, so it’s important to seek medical attention if you notice it, even if it's not accompanied by pain or other symptoms. While some causes might be relatively benign, others can be more serious and require prompt medical intervention.

1. Urinary tract infections (UTIs)

Infections in the urinary system, such as in the bladder (cystitis), urethra (urethritis) or kidneys (pyelonephritis), can cause blood in urine. UTIs often have other symptoms like a burning sensation during urination, frequent urination, or cloudy urine. UTIs can affect everyone, including children, and sometimes they need to be treated with antibiotics.

2. Kidney stones

Kidney stones, solid masses formed in the kidneys or near the urethra, can cause irritation or damage to the urinary tract, leading to bleeding. Besides blood in your urine, you will also experience intense pain in the sides of your abdomen and feel sick. It’s essential to seek medical help quickly if you are experiencing this.

3. Trauma or injury

Any trauma or injury to the urinary tract, such as a fall, accident, or physical activity, can result in blood in urine.

4. Enlarged prostate

In men, an enlarged prostate gland (benign prostatic hyperplasia) can cause haematuria. It might result in difficulties with urination along with blood in urine. Other symptoms, like frequent urination during the night, will also appear.

5. Kidney conditions

Various kidney conditions, like inflammation of the kidney's filtering units (glomerulonephritis), kidney cysts, polycystic kidney disease or kidney failure, can lead to blood in urine.

6. Cancer

Cancers of the urinary tract, like bladder, kidney, or prostate cancer, can lead to blood in urine. This is less common than other causes, but it is crucial to flag it to a GP or a urologist.

7. Non-medical reasons

Blood in urine may also appear due to other reasons that are not illness-related.

For example, certain medications, such as blood thinners (aspirin, heparin or warfarin), can cause bleeding in the urinary tract. Women may notice blood in their urine when they are on their period, and eating beetroot can also make your pee red. 

Blood in urine might also appear after an intense workout. Intense physical activity, especially high-impact exercises like running or weightlifting, can cause mechanical or microtrauma to the bladder or urinary tract. This trauma can result from repetitive movements or jarring impacts during exercise, leading to the release of red blood cells into the urine. Dehydration during exercise can also concentrate the urine, making it more acidic and potentially irritating to the bladder and urinary tract.