A signed consent form doesn’t automatically mean you gave informed consent. Under the Supreme Court’s ruling in Montgomery v Lanarkshire Health Board, your surgeon has to take reasonable care to make sure you know about the material risks of the operation and any reasonable alternatives, including doing nothing. If that didn’t happen and a risk you weren’t told about then caused you harm, you may have an informed consent negligence claim, even if the surgery itself was carried out properly. You also need to show that you would have decided differently if you’d been told, and the 3 year time limit applies.
This guide covers England and Wales. It explains what the law requires, how to tell a known complication from a failure to warn, what you have to prove and what to do next.
What does informed consent mean in law?
Informed consent means you agreed to treatment after being told what it involves, the material risks and the reasonable alternatives, and you were free and able to decide for yourself. The test comes from the Supreme Court’s decision in Montgomery v Lanarkshire Health Board, which ended the old approach of leaving it to doctors to decide how much patients should hear.
Before Montgomery, a doctor’s decision about what to tell you was judged mainly by what a responsible body of doctors would have said. Since 2015 the question is what you needed to know to make your own decision.
The court said a risk is material if a reasonable person in your position would be likely to attach significance to it, or if the doctor knows or should reasonably know that you in particular would. It also said materiality can’t be reduced to percentages. A rare risk can matter a great deal if the consequence is severe or if it threatens something you rely on, like your hands, your sight or your ability to work.
Does a signed consent form protect the surgeon?
Not on its own. A signed form is evidence that a conversation took place, but it says little about what was said. In Montgomery, the Supreme Court held that a doctor’s duty isn’t met by routinely asking for a signature. What matters is whether you were given information you could understand about the risks and alternatives, and enough time to think about it.
The General Medical Council’s guidance on decision making and consent has applied since 9 November 2020 and was updated on 13 December 2024. It treats consent as an ongoing conversation rather than a single event, and it expects doctors to record that conversation in your notes. Surgeons’ own professional guidance makes a similar point, that a form shows a discussion happened but not how good it was.
Forms tend to be weak evidence in a few familiar situations. The form was signed on the day of surgery with little time to ask questions. The risks are listed in general terms, such as infection or bleeding, without the specific risk that later affected you. Or the person who took your consent couldn’t properly discuss your operation. None of these automatically means negligence, but each gives a solicitor something to look at.
What counts as a material risk, and what else should you have been told?
A material risk is one a reasonable person in your position would want to know about, or one your surgeon knew or should have known matters to you. Your surgeon should also have discussed reasonable alternatives, including non-surgical options and having no treatment, and what could happen if you went ahead or if you didn’t.
The NHS describes valid consent as voluntary, informed and given by someone with capacity. Informed means being told about the benefits and risks, the reasonable alternatives and what happens if treatment doesn’t go ahead. In a good consent discussion you would expect the following.
- What The Procedure Involves And Why It Is Recommended
- The Material Risks, Including Rare But Serious Ones
- Reasonable Alternatives, Including No Treatment
- Any Risks That Are Specific To Your Health Or Circumstances
- Who Will Carry Out The Procedure
- Enough Time To Think Before You Decide
Your own circumstances change what is material. The Supreme Court relied on an Australian case where a patient was already blind in 1 eye and faced a small risk of losing the sight in the other. A warning that is routine for one patient can be vital for another, particularly if the risk threatens your job or your independence.
What do you need to prove?
| Element | What it means | Example |
| Duty | Your doctor had to take reasonable care to make sure you knew about material risks and reasonable alternatives | A planned operation with a recognised risk of nerve damage |
| Breach | The risk or alternative wasn’t properly explained, or was raised too late or too vaguely | A generic form listing complications with no real discussion |
| Causation | If properly told, you would have decided differently, for example by declining, choosing an alternative or delaying to get another opinion | You would have tried physiotherapy or injections first |
| Injury | The risk you weren’t told about happened and you suffered harm | Permanent nerve damage after the operation |
The causation step is where many claims are won or lost. Your own evidence about what you would have done carries weight, and it needs to fit with the records and the rest of your account. In Correia v University Hospital of North Staffordshire NHS Trust, the Court of Appeal pointed out that the claimant had never said she would have declined or deferred the operation, and that was a problem for her consent argument.
Courts have sometimes taken a more flexible approach where a patient says they wouldn’t have refused outright but would have delayed surgery or sought another opinion. That follows Chester v Afshar, where the House of Lords allowed a narrow departure from the usual causation rules. Whether it helps you depends on the facts.
It is also possible to win on consent and lose on technique. In Thefaut v Johnston [2017] EWHC 497 (QB), the High Court found for the patient on informed consent but not on negligent performance of the surgery.
Is it a known complication or a negligent failure to warn?
Both can be true at once. A complication can be well recognised and still be something you should have been told about. The question is whether the risk was material to you and whether it was properly explained. If you were warned and chose to go ahead, a known complication usually isn’t negligence. If you weren’t warned, you may have a claim.
Here is a simple illustration, not a real case. Imagine you’re offered spinal surgery for back pain. The surgeon mentions infection and bleeding but doesn’t mention a small risk of permanent nerve damage, or that you could try injections and physiotherapy first. You’re left with lasting nerve damage. The operation was carried out competently. If a reasonable person in your position would have wanted to know about the nerve risk and the alternatives, and you would have tried them first, the missing conversation can be the basis of a claim.
The reverse also happens. If your surgeon explained the risk clearly, gave you time to decide and recorded it, a bad outcome alone doesn’t create a claim. A specialist medical negligence solicitor can review your records and tell you which of these situations you’re in, before you spend time or money on it.
What to do if you think you weren’t warned
These steps help whether or not you end up making a claim.
- Write Down What You Remember Being Told And When
- Request Your Medical Records And The Signed Consent Form
- Keep Any Patient Leaflets Or Letters You Were Given
- Note Who Else Was At The Consultation
- Keep A Record Of Your Symptoms And Treatment Since The Operation
- Speak To A Solicitor Before The Time Limit Runs Out
Write your account down early. These cases often turn on what was said in a short conversation, and memories fade. Anyone can ask for their medical records through a subject access request, and organisations usually have 1 month to respond. A solicitor can also ask for them on your behalf.
A complaint to the hospital or PALS can run alongside a legal claim and can be a useful source of answers. It doesn’t stop the time limit running, so don’t wait for the outcome before you take advice.
How long do you have to claim?
Generally 3 years from the date of the treatment, or from the date you first knew you had a significant injury that could be attributed to it, if that is later. The rules are in section 11 of the Limitation Act 1980. The court can sometimes allow a late claim, but it uses that discretion rarely and you shouldn’t plan around it.
Different rules apply in some situations. For a child, the 3 years doesn’t start until their 18th birthday. If the patient lacks the mental capacity to bring a claim, time generally doesn’t start to run until they recover it. If the patient has died, proceedings usually need to start within 3 years of the date of death.
Because records need to be gathered and expert evidence obtained before a claim can be issued, it is sensible to take advice well before the deadline.
Funding your claim and other legal help
Medical negligence claims need expert evidence, which makes them more involved than most injury claims. We can normally act on a no win no fee basis, and we will explain in writing how fees and costs work before you decide whether to go ahead.
A failed operation can raise other questions too.
- Surgery That Caused Life Changing Injuries Is Handled By Our Serious Injury Solicitors
- If Your Original Injury Was An Accident, Our Personal Injury Solicitors Can Advise On That Claim
- If That Injury Happened At Work, Our Accident At Work Solicitors Can Help
- If Your Recovery Is Putting A Strain On Your Relationship, Our Family Law Solicitors Can Advise
- If A Relative Is Recovering In A Care Home, Our Care Home Negligence Claims Team Can Help
- If A Loved One Has Died After Surgery, Our Wills And Probate Solicitors Can Help With The Estate
- If You Now Need Long Term Care, Our Later Life Services Team Can Advise On Care Fees Planning
Frequently asked questions
Can you sue a doctor for lack of informed consent?
Yes, if you can show you weren’t told about a material risk or a reasonable alternative, that you would have decided differently if you had been, and that the risk then caused you harm. The claim is brought in negligence. A signed form doesn’t prevent it, although the discussion recorded in your notes will be closely examined.
What is the difference between a consent claim and a negligent surgery claim?
A negligent surgery claim says the operation was carried out below a reasonable standard. A consent claim says you weren’t given the information you needed to decide whether to have it. They are separate arguments, and a claim can succeed on 1 and fail on the other.
Does a very small risk have to be mentioned?
Possibly. The Supreme Court said materiality can’t be reduced to percentages. A small risk of a severe or life changing outcome can still be material, especially if it matters to your work or daily life. The answer depends on the risk, the consequence and what your surgeon knew about you.
Can I change my mind after signing a consent form?
Yes. You can withdraw consent at any point before the procedure, even after you have signed. If you were pressured to go ahead or weren’t given the time you needed, tell your care team and keep a note of what was said.
Talk to Mark Reynolds Solicitors
If you think you weren’t told about the risks or alternatives before surgery, speak to us before the time limit becomes a problem. Call us on 0800 002 9577 or contact our team for a free, no obligation chat. Our medical negligence team is based in our Warrington office, and we’re happy to meet you at home or at our Leigh, Liverpool or Runcorn offices.