There is no specific test for Parkinson’s disease, and this can make it difficult to diagnose, especially in the early stages. However, certain signs and symptoms may indicate that Parkinson’s is present.

The main symptoms of Parkinson’s disease (PD) are tremor, slow movement, and rigidity, or stiffness. The person may also experience pain and difficulty sleeping, among other changes.

These happen because of changes in the brain, and especially a clumping of certain types of protein and low levels of dopamine in the brain.

Other conditions can cause similar symptoms. Examples include dementia with Lewy bodies, progressive supranuclear palsy, and some types of stroke. Some antipsychotic medication, exposure to certain toxins, and a head injury can also cause similar symptoms.

Getting an accurate diagnosis of PD can help to improve the outlook for the condition. If a person has treatment before the symptoms become severe, medication can slow or help to prevent some changes.

How does a doctor diagnose Parkinson’s?

Genetic factors for parkinsons
The doctor will consider any known genetic factors for or family history of Parkinson’s disease.

A doctor will ask the person about their signs and symptoms, how they feel and how and when they first started.

They will carry out a physical examination, look at the individual’s medical history, and they may recommend some tests to rule out other conditions.

The doctor will ask about:

  • any existing conditions
  • any drugs the person is taking
  • whether there has been exposure to certain chemicals
  • if any close family members have or have had Parkinson’s
  • if the person has any known genetic factors that might increase the risk

Some early predictors for PD include a loss of the sense of smell and sleeping problems, especially REM sleep disorder.

The early symptoms can be similar to those that occur with other conditions. However, if a doctor suspects PD, they will probably refer the patient to a specialist in neurology or to a Movement Center. Major academic medical centers often have these.

Assessing the symptoms

A neurologist will evaluate the person’s motor function, or movement.

These include:

  • walking and gait
  • coordination and balance
  • some simple hand tasks
  • agility of the legs and arms
  • muscle tone

The doctor may also check their sense of smell and ask if they experience any pain.

They may prescribe a medication for Parkinson’s disease, for example, levodopa, which increases dopamine levels in the brain. If symptoms improve, this may indicate that PD is present.

Main symptoms

If a person has two of the four main symptoms of PD over a certain period of time, a doctor will consider PD, and they may recommend some tests.

These symptoms are:

  • tremor or shaking
  • slowness of movement
  • rigidity or stiffness of the arms, legs, or trunk
  • problems with balance and coordination, possibly leading to falls

Diagnostic tests

The doctor may order the following tests:

Blood test: This can help to rule out other conditions, such as abnormal thyroid hormone levels or liver damage.

MRI or CT scan: A scan can check for signs of a stroke or brain tumor. If there are no signs of a stroke or brain tumor, most MRI or CT scans of people with PD will appear normal. A person with a normal brain scan but symptoms of PD may have PD.

Positron emission tomography (PET) scan: This is an imaging test that can sometimes detect low levels of dopamine in the brain. PET scans are expensive, and not all hospitals offer them, so this option is not always available.

Single-photon emission computerized tomography (SPECT) scan: This is also called a dopamine transporter (DAT) scan.

Whatever the results of the scan, the doctor will primarily consider the person’s signs and symptoms when making a diagnosis.

What indicates Parkinson’s?

A diagnosis of PD is more likely if:

  • two of the four main Parkinson’s symptoms are present now or have been present at some time
  • symptoms started on just one side of the body
  • tremor shaking is more evident at rest
  • scans and tests rule out other causes
  • a Parkinson’s drug, such as levodopa, produces a strong, positive response

The doctor may need to observe the patient for some time before deciding that symptoms are consistently present and to rule out any other conditions that may be causing the symptoms.

Diagnostic criteria

As PD progresses, it becomes easier to recognize the symptoms but also harder to prevent or slow the changes through medication. For this reason, doctors are keen to diagnose the condition as early as possible.

MRI or CT scan
An MRI or CT scan can help to distinguish Parkinson’s from other conditions that may have similar symptoms, such as a stroke.

In 2016, experts developed new criteria for diagnosing early-stage (or prodromal) PD.

These involve:

1. Assessing the probability that the diagnosis will be PD, for example, by considering the person’s age.

2. Assessing the variables, including:

  • whether the person is male or female
  • environmental risks, including caffeine use, and smoking
  • genetic factors, such as family history or genetic test results
  • early signs and symptoms, for example, constipation, loss of a sense of smell, difficulty with movement
  • results of scans and other diagnostic tests

3. Calculating the results: The doctor multiplies the factors together and compares the result with a threshold measure.

If the comparison shows a likelihood higher than 80 percent that PD is present, the doctor will diagnose the early stages of PD.

A person with a 75–80 percent result will have less specific symptoms that may or may not relate to PD, such as constipation and depression.

A person with 95–97 percent will probably be experiencing REM sleep behavior disorder, a symptom that is more closely linked with PD.

Staging PD

The doctor will enter the results of the medical examination into a table, called the United Parkinson’s Disease Rating Scale (UPDRS).

The UPDRS is useful for tracking and predicting an individual’s progression through the stages of PD. It enables doctors to assess and document comprehensively the results of patient assessments.

It also means they can compare data entered with future follow up examinations or communicate data with other neurologists.

What to expect

The doctor will check for physical symptoms, such as tremor.
The doctor will check for physical symptoms, such as tremor.

When you see a doctor about your symptoms, they will probably want to know:

  • What do the symptoms feel like?
  • When did they start, and did the person experience any other unusual event around that time, such as an infection, head trauma, or stroke.
  • When are they worse or better?
  • Does anything help to relieve them?
  • Are you taking any medications?

If the diagnosis is PD, they will discuss what this is likely to mean for you and the treatment options that are available.


Hearing that you or another person has PD can be a life-changing event. Support from your health workers, friends, and family will be important.

It can help to find out as much information as you can about what causes PD, what to expect, what kind of support is available, and what kind of treatment your insurance will cover.

Communicating with your doctor and those around you is also likely to be important.

You may find it helpful to get in touch with a local or online community group for people with PD and their loved ones. A doctor will be able to advise you on this.

National Disease-Specific Organizations, such as the Parkinson’s Foundation, can also offer advice and information.