The short answer
- Heat and tiredness are not the same as MS getting worseAround six in ten people with MS find heat brings old symptoms back for a few hours. It settles with cooling and rest, and it is not new damage.
- An infection can look exactly like a relapseA urinary tract infection is common in MS and can cause the same sudden decline as a true relapse. A GP can test for it in minutes.
- Stiffness and balance changes raise the risk of a fallSpasticity and balance problems build gradually, and a safer home and regular movement both reduce the risk.
- You are one part of a wider teamAn MS nurse specialist, a GP and a physiotherapist each cover ground a carer should not try to cover alone.
Checked against MS Society and MS Trust guidance, September 2026.
Why symptoms change
Why a bad day is not always MS getting worse
More than 150,000 people in the UK live with MS, and around 7,100 more are diagnosed every year. Most start with relapsing remitting MS, where symptoms flare up and then ease off, sometimes for months at a time; some go on to a more steadily progressive form. What makes the condition hard to plan around is that three quite different things can all look like the same bad day.
The number of people living with MS in the UK has risen sharply, MS Trust reports, largely because of better diagnosis and people with MS living longer, rather than more people developing it.
Heat or fatigue
How it starts
Comes on with warm weather, a hot bath, exercise, or a tiring day. Old symptoms come back rather than new ones appearing.
How long it lasts
Hours. It settles once the person cools down and rests, MS Trust says, and does not need a doctor.
What helps
A cooler room, a fan, a cold drink, loose clothing, and a rest. No new damage is being done.
An infection, often a UTI
How it starts
Comes on over a day or so, sometimes with a raised temperature, pain passing urine, or urine that looks cloudy or smells strong.
How long it lasts
Until it is treated. Left alone it can trigger worse symptoms or, rarely, become serious.
What helps
A GP appointment and a urine test. Tell them it may be masking as MS getting worse, since that is a common mix-up.
A true relapse
How it starts
A symptom that is new, or clearly worse than before, lasting more than 24 hours with no infection or heat to explain it.
How long it lasts
Days to weeks, sometimes longer, and it usually needs the MS team to confirm and to treat.
What helps
A call to the MS nurse or GP. Steroids can shorten a relapse, but only a clinician can prescribe them.
Knowing which of the three you are looking at changes what to do next. Heat and fatigue need a cooler room and a rest. An infection needs a GP appointment. A true relapse, a new or clearly worse symptom lasting more than a day with nothing else to explain it, needs the person's MS nurse or GP to confirm it, and it is not something a carer is expected to diagnose. If you are ever unsure, treat that uncertainty as reason enough to call someone who can check, rather than waiting to see if it passes.
Heat and fatigue
Managing heat sensitivity and fatigue day to day
Warmth affecting MS symptoms has a name, Uhthoff's phenomenon, and MS Trust says it happens because heat makes it harder for damaged nerves to carry a signal. It is temporary and reverses within hours of cooling down, but it is also one of the most common reasons a planned activity has to change on the day.
Heat sensitivity and MS, from MS Trust, explains that around six in ten people with MS notice it, and that it is not a sign of new damage.
Stay cool
Pace the day
Protect sleep
Keep meals and fluids regular
Movement and falls
Supporting movement as stiffness and balance change
Muscle stiffness, spasms and balance problems tend to build up gradually rather than arrive all at once, which makes them easy to underestimate until a fall happens.
Stiffness and spasms (spasticity)
Balance and coordination
Weakness or foot drop
Confidence after a fall
A safer home helps regardless of the cause: clutter and trailing cables cleared, grab rails where they are needed, good lighting on the stairs, and a clear route to the bathroom at night. Risk assessment for carers has a template for working through a home room by room, and moving and handling when working for private clients is worth reading before you help with a transfer.
Bladder and infections
Spotting a urinary infection before it causes a bigger problem
MS Trust says bladder symptoms affect around three in four people with MS, usually either needing the toilet urgently and often, or the opposite, finding it hard to empty the bladder fully. That second problem, urine sitting in the bladder, is also what makes a urinary tract infection more likely.
Worth a call to the GP
- A raised temperature or feeling generally unwell
- Pain or a burning feeling passing urine
- Urine that looks cloudy or smells strong
- A sudden increase in confusion, weakness or stiffness within a day or so
Common MS bladder changes
- Needing the toilet more often or with more urgency
- An occasional leak
- A slow or interrupted flow
- Waking once or twice in the night to use the toilet
Cutting down on fluids does not help and risks dehydration, which brings its own confusion and fatigue, so keep encouraging normal drinking and offer the toilet promptly. Constipation makes bladder symptoms worse too, since a full bowel presses on the bladder. Managing your client's incontinence and writing a continence care plan go further into day to day support.
Thinking and mood
Helping with brain fog and low mood without taking over
Many people with MS describe what they call brain fog: thinking or memory that feels less reliable than it used to, often worse when they are tired, stressed or unwell. The unpredictability of the condition itself, good weeks followed by a bad one with no clear reason, also takes a toll on mood.
Keep a routine and a memory point
One thing at a time
Watch for low mood as well as forgetfulness
Company matters
If memory or confusion becomes a bigger and more constant problem rather than something that comes and goes with tiredness, managing clients with dementia covers approaches that can help alongside this, whatever the underlying cause.
Building the team
The people worth knowing before you need them
Nobody expects a carer to manage MS alone, and knowing who to call before a bad day saves time when one happens.
An MS nurse specialist
The GP
A physiotherapist or occupational therapist
MS Society's helpline
Disease-modifying therapies, the medicines that reduce how often relapses happen, are prescribed and reviewed by the MS team, not by a carer, and PrimeCarers carers are not expected to manage or administer medication as part of the introduction. What a carer can do is notice a change worth reporting, keep a written note of it, and pass it on to whoever the family has asked you to update. Carer training for private carers and moving and handling when working for private clients are worth reading before your first visit with a new client, and supporting someone through an unpredictable condition can be draining in its own way, so MS Society's helpline is there for you too, not only for the person you support.
Questions
Questions carers ask about supporting someone with MS
Multiple sclerosis happens when the immune system damages the coating around nerves in the brain and spinal cord, which disrupts the signals those nerves carry. More than 150,000 people in the UK live with it. Most people are diagnosed with relapsing remitting MS, where symptoms flare and then ease, sometimes for months, before some go on to a more steadily progressive form. Multiple sclerosis, on nhs.uk.
Heat and tiredness bring back old symptoms for a few hours and settle with cooling and rest. An infection, often a urinary tract infection, tends to come with a raised temperature or pain passing urine and needs a GP. A true relapse is a new or clearly worse symptom lasting more than 24 hours with nothing else to explain it, and it needs the MS team to confirm. Urinary tract infections, from MS Trust.
Tell the family or whoever oversees the arrangement, and encourage a call to the GP or MS nurse rather than waiting to see if it passes. A relapse is confirmed and treated by a clinician, sometimes with steroids to shorten it, and a carer is not expected to make that call alone. Managing relapses, from MS Society.
It usually helps. MS Trust recommends around two and a half hours of moderate activity a week, such as walking, swimming or light resistance work, to support mobility, sleep and fatigue. Exercising somewhere cool and in shorter bursts avoids triggering the heat response that can make symptoms feel worse temporarily.
Not in a fixed way. Relapsing remitting MS, the most common type at diagnosis, can stay stable for long periods between relapses, and disease-modifying therapies reduce how often relapses happen. Some people go on to a secondary or primary progressive form where symptoms build more steadily, but the pace and pattern vary a great deal from person to person.
No qualification is legally required to work as a private carer, but knowing the difference between heat, an infection and a relapse, covered on this page, is worth learning before a bad day rather than during one. Carer training for private carers covers the rest of what is worth learning early.
MS Society runs a free, confidential helpline on 0808 800 8000, 9am to 5pm Monday to Friday except bank holidays, for carers as well as people with MS, and MS Trust's website covers individual symptoms in more depth. Carer resources has the rest of PrimeCarers' guides on training and day to day care.