How Doctors Diagnose Parkinson's Disease

Medically Reviewed By William C. Lloyd III, MD, FACS
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It’s not unusual to have some symptoms of Parkinson’s disease without a definite diagnosis. That’s because Parkinson's is hard to diagnose in its early stages. There is no blood test for the disease. It may take years for the diagnosis to become clear. 

You may start by seeing your primary care doctor.  But the best doctor to diagnose Parkinson's is a movement disorder specialist. That's a neurologist with extra training in conditions like Parkinson's. 

Symptoms Are Key to Diagnosis

A movement disorder specialist will ask about your symptoms. The doctor also will do a full neurological exam. To make a diagnosis of Parkinson's, the doctor will want to see at least two of these four symptoms: 

  • A shaking, or tremor, in your hands and arms when your arms are extended or resting
  • A slowing-down of movement, called bradykinesia
  • Trouble keeping your balance
  • Stiffness in your arms and legs, called rigidity

The doctor may look at your face to see how it shows emotion. The doctor also might ask you to get into and out of a chair and to walk around the room. The doctor may put all symptoms into what's called the United Parkinson’s Disease Rating Scale. Doctors use this to watch how your symptoms change over time. Other symptoms that go along with Parkinson's include:

These types of symptoms may not be as noticeable as movement symptoms. Even if you think it it’s not related, let your doctor know about anything you’re experiencing that is new or out of the ordinary for you.

Response to Medication Can Matter

Other movement disorders can act like Parkinson's. That makes it hard to know for sure whether you have the disease, even after a complete exam. However, the loss of dopamine causes Parkinson's. It's a chemical made by brain cells. It is important for movement. 

For this reason, your doctor may want you to take a dopamine replacement drug called levodopa. Then your doctor will watch to see whether your symptoms improve. If you get better on levodopa, it's more likely that you have Parkinson's. 

Brain Imaging Can Help With Diagnosis

Doctors use two tests that take detailed pictures of your brain. Each one may help your doctor make a diagnosis. These tests are: 

  • PET scan: This shows how your brain functions. It shows how the brain uses sugar. This scan can help tell the difference between Parkinson's and dementia
  • DaTscan: This shows problems with brain cells that make dopamine. Healthy brain cells light up during the test. Cells without enough dopamine appear dark. This scan can help your doctor tell the difference between Parkinson's and a brain disease called essential tremor.

Imaging studies are a newer way to diagnose Parkinson's. However, not every healthcare facility can do them. It takes an experienced doctor to interpret the scans accurately. These scans also can be very expensive. Be sure to check with your insurance company ahead of time to see whether you are covered and what your out-of-pocket costs will be. 

Consider the Age and Time Factor

Doctors also keep in mind other factors when diagnosing Parkinson's. For instance:

  • The disease is not common in people younger than 50.
  • Diagnosing Parkinson's can be tricky and may take time.
  • Other diseases can cause similar symptoms. Your doctor will try to rule out other diseases that mimic Parkinson's such as stroke
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Aug 4
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.

  1. Diagnosis. Parkinson’s Disease Foundation,

  2. How does your doctor make a PD diagnosis? National Parkinson Foundation,

  3. NINDS Parkinson’s Disease Information Page. National Institute of Neurological Disorders and Stroke, March 2014,

  4. DaTscan for Parkinson’s. National Parkinson Foundation.