Clinical Global Impression Scale (CGI)

Use the Clinical Global Impression Scale (CGI) for your practice to evaluate a patient’s mental illness, the severity of their symptoms, and the effectiveness of the medicine provided to them!

By Audrey Liz Perez on Aug 2, 2025.

Fact Checked by Ericka Pingol.

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What is the Clinical Global Impression Scale (CGI)?

The (or the CGI Scale for short) is an easy-to-use assessment tool developed for clinicians to quickly evaluate an adult patient with mental illness based on a clinician’s overall experience with adult patients who have the same or similar illness. Essentially, it evaluates the effects of mental health treatments amongst psychiatric patients.

It comes in the form of a three-item questionnaire in which they will evaluate the following:

The severity of the patient’s mental illness at this time, which they will rate between 0 to 7. This portion is known as the CGI-S (Clinical Global Impression - Severity).
The improvement of the patient since they first were admitted for their mental health illness, which they will rate between 0 to 7 as well. This portion is known as the CGI-I (Clinical Global Impression - Improvement).
The effectiveness of the drug administered to the patient. This portion is known as the Efficacy Index.

Given its length, any health practitioner using this scale will be able to accomplish it quickly, especially if they are experienced with their work and are familiar with the patient they are handling.

Clinical Global Impression Scale (CGI) Template

Clinical Global Impression Scale (CGI) PDF Template

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How to use the Clinical Global Impression Scale (CGI)

Rate the CGI-S (severity of illness).

The first thing that the healthcare professional needs to do is rate the severity of their patient’s mental illness at this current time.

The rating is between 0 to 7 and these are the designations per number:

0 = not assessed
1 = normal, not at all ill
2 = Borderline mentally ill
3 = mildly ill
4 = moderately ill
5 = markedly ill
6 = severely ill
7 = among the most extremely ill patients

Again, the practitioner should rate based on their overall clinical experience with the same population (adults who have the same or similar mental illness).

Rate the CGI-I (global improvement).

The second part of the scale will have the practitioner rate the patient in terms of how much they have improved since the first time they were admitted. The practitioner will rate them between 0 to 7 based on their judgment of whether or not their improvement is due entirely to the drug treatment provided to the patient.

Here are the rating designations:

0 = not assessed
1 = very much improved
2 = much improved
3 = minimally improved
4 = no change
5 = minimally worse
6 = much worse
7 = very much worse

Rate the Efficacy Index.

The last part of the scale is the Efficacy Index, which is divided into two parts!

The practitioner will rate the effect of the drug prescribed to the patient in terms of its effect.

The first part is selecting the term that best describes the degree of the drug’s therapeutic effect. These are the terms for this part:

Marked = Vast improvement. Complete or nearly complete remission of all symptoms.
Moderate = Decided improvement. Partial remission of symptoms
Minimal = Slight improvement which doesn’t alter the status of care of the patient
Unchanged or worse

The second part is selecting the number that corresponds to the following side effects:

None (01 = marked, 05 = moderate, 09 = minimal, or 13 = unchanged or worse)
Do not significantly interfere with the patient’s functioning (02 = marked, 06 = moderate, 10 = minimal, or 14 = unchanged or worse)
Significantly interferes with the patient’s functioning (03 = marked, 07 = moderate, 11 = minimal, or 15 = unchanged or worse)
Outweighs therapeutic effect (04 = marked, 08 = moderate, 12 = minimal, or 16 = unchanged or worse)
00 = not assessed

‍Update your care plan.

Given the context of the scale’s structure, it is meant for patients who have already been admitted and started treatment. These ratings should reflect where they are currently based on your assessment of them. While there is no global score to refer to, you have your ratings on which to base your next steps. Should you change the medicine based on the ratings you gave? Should you simply up the dosage? These are some of the questions you’ll be able to answer by using the scale.

When does one typically use the Clinical Global Impression Scale (CGI)?

As mentioned earlier, the Clinical Global Impression Scale (CGI) context is that you are assessing a patient who has already set appointments with you and has undergone treatment based on whatever care plan you have made for them.

Given that, you are typically using this to check on your patient during subsequent sessions because you will be rating them based on:

How mentally ill they are during the time you are using this scale
How much they have improved or worsened since you first admitted them and if the change is due to the prescribed medication
The therapeutic effect of the prescribed medication and its side effects on the patient in terms of affecting their functioning

While the copy we have is a replicated version of the original one, we added an Additional Comments section where you can indicate any comments you might have, like your findings, especially if you have been reusing this test a lot on the same patient.

Who typically uses the Clinical Global Impression Scale (CGI)?

The Clinical Global Impression Scale (CGI) was designed to check on patients with mental illnesses, so the following healthcare practitioners are the ones who typically use this to assess their patients:

Clinical psychologists
Psychiatrists
Mental health therapists

Any healthcare professional specializing in mental illnesses and their treatment can definitely use this for their work.

What are the benefits of using the Clinical Global Impression Scale (CGI)?

‍It is straightforward and easy to use.

The Clinical Global Impression Scale (CGI) is easy to use. You only need to rate the patient based on two prompts and then rate the prescribed medication based on its therapeutic effect and impact on the patient’s function.

The ease of use also makes it quick to accomplish. If you are handling more than one patient and have several appointments in a day, then using this scale might be beneficial because it could save you some time.

It’s a great way to monitor a patient over time.

Given that this scale is used to assess patients undergoing a mental health treatment plan who are taking medication, it is a monitoring tool that will help the practitioner determine if their patients are getting better. Practitioners can better determine what needs to be changed and maintained in the treatment plan.

It can be used to determine if the medication being used is effective or not.

Speaking of monitoring the patient and determining what should be changed or maintained in a treatment plan, this scale monitors the effectiveness of the prescribed drug being used for the treatment.

If the patient is getting better, is this the cause of the prescribed drug (this will be based on your judgment)?

Is the drug even working, to begin with? What are the side effects on the patient’s functioning?

If your assessment shows that the drug is not effective and the side effects are impacting the patient’s functioning negatively, then obviously changing the dosage or changing the prescribed medication might be more beneficial. If they are getting better and the side effects are not bad at all, then the medication should be maintained.

Commonly asked questions

It shouldn’t take you more than a minute, especially if you are highly experienced in treating mental health patients and if you are highly familiar with the patient you are evaluating. There are only three items to tackle, after all. But generally, it can be accomplished between 1-2 minutes.

Yes, it is. The scale is used generally by well-trained practitioners who have enough experience dealing with mental health patients. Of course, it’s good to point out that this scale is subjective given that the scale is answered by a healthcare practitioner observing a patient, so the ratings are based on their point of view.

For one, it is used generally by well-trained practitioners with enough experience dealing with mental health patients. The scale also focuses on a patient’s current condition and how the prescribed medicine they are taking is affecting them. The ratings will be based on factors that can be observed.

Here’s an example:

Let’s say a patient sets up an appointment a year prior to using this scale. During that time, the patient was obviously in a bad place, so they were diagnosed with a mental illness, and a treatment plan with medication was given to them.

Then, the patient comes back for a routine evaluation, and now they look so much better, showing no signs that the mental illness is affecting them, even physically. The practitioner can rate the first part of the scale with 1. If the patient says the medication is working wonders, then the rating for the second part can be either 1 or 2.

As for the last part, since the patient mentioned that the medication is working wonders and they are obviously looking better than they did when they first came to the clinic, then the therapeutic effect of the medicine can be rated as Marked. If the patient is able to function well despite taking the medicine, then the side effects portion can be rated 01 or 02.

If things are not easily observed, then that’s the reason why appointments are scheduled. The professional and the patient can discuss things to help inform the ratings.