Why Does My Lower Back Hurt? Causes and Red Flags

Lower back pain is one of the most common reasons adults see a doctor, and it can be startling how much a single awkward lift or a long day at a desk can hurt. The reassuring part is that most episodes are not caused by anything serious and get better on their own.

This guide walks through the usual causes, the patterns that point to a nerve being involved, what tends to help, and the small set of warning signs that mean you should not wait. It can help you understand what might be going on and decide on a next step, but it cannot diagnose you.

Why does my lower back hurt?

In most cases, lower back pain is mechanical, meaning it comes from the muscles, ligaments, joints, and discs of the spine rather than from disease. According to NIAMS, the most common triggers are a strain from lifting, twisting, or a sudden movement, and wear and tear that builds up with age.

Doctors often cannot point to one exact structure, and that is normal. When no specific cause is found, the label is "nonspecific low back pain", and it still tends to settle well with time and movement.

Back pain sits alongside many other everyday complaints covered in our physical health guide, and like most of them, the pattern of symptoms tells you more than the pain level does.

What are the most common causes of lower back pain?

The most common causes are muscle or ligament strain, disc problems, age-related joint changes, and posture or inactivity. Less often, the pain comes from somewhere outside the spine, such as the kidneys.

Cause	What it usually feels like	Typical pattern
Muscle or ligament strain	Aching, tight, or spasming muscles on one or both sides	Starts after lifting, twisting, or unusual activity; improves over days to weeks
Herniated or bulging disc	Back pain that may shoot into the buttock or leg	Often worse sitting, bending, coughing, or sneezing
Spinal arthritis (degenerative changes)	Stiffness, especially in the morning	Gradual, comes and goes, more common after 50
Spinal stenosis	Leg aching, heaviness, or tingling when walking	Eases when you sit or lean forward, such as on a shopping cart
Kidney stone or infection	Deep pain in the side or flank, may come in waves	Often with fever, painful urination, or blood in urine
Compression fracture	Sudden, sharp pain in the middle or lower back	After a fall, or with minor strain in people with osteoporosis

Strain and sprain

A strain is a stretched or torn muscle, and a sprain is a stretched or torn ligament, the tough bands that hold bones together. Both cause pain, stiffness, and sometimes spasms, and both usually heal within a few weeks.

Disc problems

Discs are the rubbery cushions between the bones of the spine. A herniated disc happens when the soft center pushes out through the tougher outer layer, and if it presses on a nearby nerve it can cause leg pain, numbness, or tingling.

Posture and long hours of sitting

Sitting for long stretches does not damage the spine on its own, but staying in one position can leave the back stiff and sore. Breaking up sitting time with short movement breaks, as described in what actually helps when you sit all day, often does more than chasing a perfect posture.

Is it a pulled muscle or something with a nerve?

A pulled muscle usually stays in the back, while a pinched nerve tends to send pain, tingling, or numbness down the leg. That leg pain pattern is called sciatica, after the sciatic nerve that runs from the lower back down the back of each leg.

According to MedlinePlus, sciatica most often follows a herniated disc or narrowing of the spinal canal. It typically affects one leg, can feel like burning or electric shocks, and often hurts more than the back itself.

Feature	Muscle strain	Nerve irritation (sciatica)
Where it hurts	Lower back, sometimes the buttock	Back and buttock, running below the knee
Type of pain	Dull ache, tightness, spasm	Sharp, burning, or shooting
Other sensations	Usually none	Tingling, pins and needles, numbness
Weakness	No true weakness, just pain with movement	Sometimes, such as a foot that drags or catches
Usual outlook	Better in days to a few weeks	Often improves over weeks; persistent weakness needs review

Sciatica on its own is usually not an emergency, and many people improve without surgery. Weakness that is getting worse, or numbness in the groin area, is different and is covered in the red flags below.

How long does lower back pain usually last?

Most acute lower back pain improves noticeably within a few days to a few weeks. Doctors call pain acute when it has lasted less than about four weeks and chronic when it lasts 12 weeks or longer.

According to MedlinePlus, many people feel better within the first month, though the back can stay a little stiff or sore for longer. Flare-ups are common, so having a second episode does not mean something new has gone wrong.

Pain that lasts beyond a few weeks, keeps returning, or steadily worsens is worth a visit to your primary care provider, who can check for causes that need a different approach.

What can you do at home for lower back pain?

Staying gently active is the single most helpful thing for most people with a new episode of back pain. Bed rest used to be standard advice, but staying in bed for more than a day or two tends to slow recovery.

• Keep moving within comfort. Short, frequent walks are a good starting point, and regular walking is one of the easiest habits to keep once the pain settles.
• Use heat or cold. Some people prefer ice in the first day or two and heat after that; use whichever feels better, wrapped in a cloth, for about 20 minutes at a time.
• Consider an over-the-counter pain reliever. Acetaminophen or a nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen or naproxen may help. Follow the label and check with your doctor or pharmacist if you have stomach, kidney, heart, or liver problems or take other medicines.
• Change position often. Get up from sitting every 30 to 60 minutes, and sleep in whatever position is comfortable, such as on your side with a pillow between your knees.
• Return to normal activities gradually. Avoid heavy lifting and twisting for a short time, then build back up rather than waiting to be completely pain free.

How can you lower the chance of it coming back?

Regular physical activity and stronger core and hip muscles appear to lower the chance of future episodes, though no approach prevents every flare. The Physical Activity Guidelines for Americans recommend 150 to 300 minutes of moderate activity a week plus muscle-strengthening work on at least two days.

Strength work does not have to mean heavy weights. A simple, progressive routine, like the one in a beginner framework for strength training, builds the muscles that support your spine. Lifting with your legs, keeping loads close to your body, and avoiding twisting while you lift all reduce strain.

Rest and recovery matter too. Sleep, managing stress, and not jumping straight from inactivity to an intense weekend project all reduce the chance of a strain.

What are the red flags for lower back pain?

A small number of symptoms suggest something more serious, such as nerve compression, infection, a fracture, or cancer, and they need prompt medical attention. Doctors call these "red flags".

• Numbness in the groin, genitals, buttocks, or inner thighs (the area that would touch a saddle)
• New trouble controlling your bladder or bowels, or being unable to urinate
• Weakness in one or both legs that is getting worse, or a foot that drags
• Fever or chills with back pain, especially after recent infection, surgery, or injecting drugs
• Back pain after a significant fall, car crash, or other injury
• A history of cancer, unexplained weight loss, or pain that is worse at night and not eased by rest
• Long-term steroid use or known osteoporosis, which raises the chance of a fracture

The first two items can be signs of cauda equina syndrome, a rare condition in which the bundle of nerves at the bottom of the spinal canal is squeezed. It needs emergency care, because delays can lead to permanent problems.

When should you see a doctor or call 911?

Call 911 or go to the emergency room right away if back pain comes with numbness in the saddle area, loss of bladder or bowel control, rapidly worsening leg weakness, or a serious injury. Sudden, severe pain in the back or abdomen with lightheadedness or fainting also needs emergency care, as it can signal a problem with the aorta, the body's main artery.

Make a same-day or next-day appointment with your doctor or visit urgent care if you have back pain with fever, painful urination or blood in your urine, or pain after a minor fall if you are older or have osteoporosis.

Talk to your primary care provider if pain lasts more than a few weeks, keeps you awake, keeps coming back, or comes with leg numbness or tingling that is not improving. They may suggest physical therapy, which teaches exercises tailored to your back. Imaging such as an X-ray or MRI is usually not needed early on unless red flags are present, because many changes it shows are common in people without pain.

If you are unsure whether your symptoms are urgent, it is always reasonable to call your doctor's office or a nurse advice line and describe what is happening.