Because no single, one-stop, diagnostic test exists to determine whether a person has Parkinson's disease, the diagnostic process is complex and involved. When your healthcare provider suspects that you may have Parkinson's, the most common degenerative neurological disease after Alzheimer's, they'll look at your symptoms and medical history as well as performing physical and neurological exams. Though your primary care provider — usually a family doctor — will almost always serve as your first point of call, a neurologist should be involved in making the final diagnosis. 
Recognizing the possible symptoms of Parkinson's
The symptoms of Parkinson's disease can be separated into motor (affecting movement) and non-motor symptoms, both of which increase in severity over time. Although the way in which Parkinson's disease progresses and the symptoms patients will experience do differ from person to person, the disease's general patterns are predictable enough that doctors have been able to develop a scale of severity, from Stage 1 (mild) to Stage 5 (severe).
- Tremors — this symptom, widely considered the most characteristic of Parkinson's, begins on one side of the body, in one arm, hand, or even finger, or in one foot or leg. Tremors can also affect the facial muscles, in which case they'll likewise initially occur unilaterally (on one side of the face). This "shaking" tends to be worst during periods of rest when you're not doing anything else, and a tapping of the thumb and index finger may be the only thing that gives it away.
- Bradykinesia is the medical term for atypically slow movement, another very well-known sign of Parkinson's disease. This can lead to an unusual, shuffling, gait, cause everyday tasks such as getting dressed or brushing your teeth much longer to complete, and may cause intense, "mask-like" facial expressions. Shrinking handwriting, a common early symptom of Parkinson's, also falls into this category. Your speech may become slurred, and the volume of your voice may change, as well.
- Stiffness (rigidity). Just like Parkinson's disease, suffering from stiffness becomes more common as people get older — meaning this is a symptom both patients and doctors can easily attribute to nothing but age.
- Posture changes. Difficulty maintaining balance is one of the main symptoms of Parkinson's in later stages, but even early on, the disease can cause subtle postural changes.
Non-motor symptoms during the earlier stage of Parkinson's disease can, meanwhile, include :
- A loss of your sense of smell, something that can affect a patient years before they present with other symptoms.
- Disordered sleep, particularly being abnormally active as you sleep and even "acting out" your dreams. While patients may not be aware this is happening, their partners, if they have them, won't be able to miss these symptoms!
- Many Parkinson's disease patients suffer from depression and anxiety. In the later stages of the disease, delusions and psychosis are not uncommon.
- Constipation and straining during bowel movements are other potential early warning signs.
- Many Parkinson's patients suffer from low blood pressure, which will make them feel dizzy and faint.
Your family doctor will likely ask you:
- About the nature, severity, and duration of your symptoms, as well as when they first started.
- About pre-existing medical conditions you're aware you have as well as about any medications you're taking — if your family doctor is already well aware of these, they'll just ask you to confirm.
- About exposure to certain chemicals (such as pesticides and fungicides) and metals (like lead and iron) during your lifetime.
- Though most cases of Parkinson's don't run in families, this can sometimes happen — so expect your doctor to ask you whether you have close relatives with the disease.
The diagnostic process: What will your neurologist ask you if they suspect Parkinson's?
The early symptoms of Parkinson's disease can be caused by other conditions as well, so your neurologist will seek to rule these in or out. The following differential diagnoses will be considered :
- Bradykinesia: Drug-induced Parkisinson ism, vascular Parkinsonism — Parkinsonism referring to the motor symptoms seen in Parkinson's disease.
- Tremor: Essential tremor, intention tremor (cerebellar tremor), tremors are the result of side effects of medications you are taking (particularly antidepressants) or as the result of alcohol abuse.
If your neurologist uses the Unified Parkinson's Disease Rating Scale (UPDRS), the most common rating scale, your neurological examination will consists of four distinct parts where your neurologist suspects Parkinson's disease :
- The behavioral and cognitive aspects of Parkinson's disease
- The motor symptoms you're suffering from and how they impact your life
- A motor examination, during which you'll be asked to engage in daily activities such as walking or writing to assess your abilities.
- Complications of treatment you are receiving.
The Movement Disorder Society has updated the UPDRS, and this revised version, known as the MDS-UPDRS , is now used more and more often. It includes numerous questions, some of wich your neurologist will ask you and then assess, and some of which you will be asked to fill in yourself on questionnaire — a caregiver or relative can help you if needed. These questions are answered on a scale of zero to four, depending on the extent to which they apply to a patient.  Some physicians will also use Adenbrook's Cognitive Examination, as Parkinson's often goes hand in hand with dementia in the later stages. 
Questions that you and/or a caregiver can answer orally include those relating to your current symptoms:
- What symptoms initially led you to seek medical attention?
- When did you first notice them?
- Have you noticed under what circumstances they are worst, and under what circumstances they tend to get better?
- Have they changed in nature or severity since you first noticed them?
- What everyday activities are you struggling with? (This may include getting dressed, brushing your teeth, writing, doing the dishes, and eating.)
- Do you experience tremors?
- Where in your body?
- How often, and under what circumstances? (Are they worse at rest?)
- Are you abnormally active during sleep? (This will often require the help of a partner to ascertain.)
- Do you find it hard to turn over in bed?
- How is your sense of smell?
- Does your body do what you want it to, or do you find it is no longer cooperating with you?
- Are you depressed? (This may also be asked in a more round-about way, such as to what extent you enjoy socializing, engaging in hobbies, what your general outlook on life is, and so on.)
- Do you have trouble remembering things, or do you often misplace objects?
- Have you had trouble maintaining balance?
- Have you experienced any falls recently?
- Do you need a cane, a walker, or to hold onto a rail to prevent falls?
- Have you "frozen" (or "gotten stuck") while attempting daily activities?
- Do you have any difficulty swallowing?
- Do you feel stiff? Only in the morning or all day long?
- Is walking difficult?
- Do you frequently suffer from constipation?
- Or straining during bowel movements?
- Do you experience urinary urgency?
- Do you have any strong impulses that are difficult to resist?
- Do you suffer from fatigue?
- Do you often feel dizzy or faint?
- Is it difficult for you to get up when you were sitting or laying down?
- Do you suffer from any hallucinations or delusions? (It is, of course, typically very difficult for people affected by these things to realize they have them — this question is, as such, often better answered by someone else who knows you well.)
Questions relating to risk factors for Parkinson's disease (as well as differential diagnoses) may include:
- What medical conditions have you suffered from in the past, and which medical conditions do you currently have?
- What medications are you using and have you used in the past?
- Have you experienced side effects from any of the medications you have used or are currently using?
- Does anyone in your family suffer from Parkinson's disease? (Around 15 percent of patients have a close relative with the disease.)
- Have you, to your knowledge, been exposed to chemicals or metals, such as paraquat, manet, lead, or iron?
- Have you suffered any head trauma in the past?
- Several genetic mutations have been associated with Parkinson's, and your neurologist may ask you if you are aware of having any of these.
Questions relating to the physical portion of your examination and your neurologist's assessment of your cognitive state may, in one form or another, include:
- Can you talk to me? (Your specialist is assessing the volume of your voice. They'll start doing this the minute they ask you how you are as you walk through the door — the question will probably not be as blunt as "Can you talk to me?", but that's the general idea.)
- Can you write something for me? (Parkinson's often features abnormally small and crowded handwriting.)
- Can you walk a bit? (This is to assess your gait and balance.)
- Can you follow this object with your eyes? (This is part of any neurological exam.)
- Can you blink? (More likely though, your neurologist will simply observe your facial expression and how often you blink.)
- How difficult is it for you to grab this object? (Your neurologist is looking at your ability to move, and your speed, keeping an eye out for "jerking" movements associated with Parkinson's.)
- Can you move your arms all the way around?
- Can you stand up? (To assess your posture and balance.)
- Can you make a tight fist?
- What is your date of birth? (And similar questions to test your memory, such as the name of the current leader of your country.)
- Can you read this bit of text or sequence of numbers and are you then able to read it back to me? (This looks at your short-term memory.)
- The neurologist may give you a letter of the alphabet and ask you to come up with as many words as possible starting with this letter.
- Do you feel this? (Your neurologist may prick, prod, or touch you to find out whether you can feel it.)
- How tense are your muscles? (A physical exam offers answers.)
- Are your movements abnormally slow? (Your neurologist will ask you to move and will observe the way in which you do so.)
Just as your neurologist will ask you plenty of questions to help them during the diagnostic process, you should feel free to send ample questions in their direction as well. You'll most likely be after information about Parkinson's disease, your prognosis, and how the disease is generally managed. You may also want to know more about your doctor — how much experience do they have with diagnosing and treating Parkinson's, and are they aware of the latest scientific data?
It can help to prepare yourself for the kinds of questions a neurologist will ask you — as well as the questions you have for them — before your appointment. In addition, it is very helpful to have someone else who knows you well with you, even if you are very physically independent and do not believe you are impacted by any cognitive symptoms. Another pair of eyes (and another brain) might have noticed changes in you that you haven't yourself, and their answers can provide your neurologist with valuable insights.