diagnose someone with + illness
Naming a medical condition
This is the standard pattern in active and passive sentences.
Doctors diagnosed him with pneumonia.
Diagnose with, in, by, at or after?
Diagnose with is used in passive structures, while diagnose by refers to methods. Other prepositions usually add time or place information.
Quick answer
Common patterns
Doctors diagnose someone with a condition. In passive sentences, a person is diagnosed with a disease. Diagnose by refers to the method used. In, at, and after are usually separate time or place phrases, not fixed combinations.
She was diagnosed with asthma.
The condition was diagnosed by a blood test.
The condition was diagnosed by a blood test.
Choose the pattern by meaning
These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.
diagnose by + method
Explaining how the diagnosis was made
Use by for tests, scans, or procedures.
The disease was diagnosed by MRI scan.
diagnose in + place/group
Adding location or context
In is usually an adjunct showing where diagnosis happens.
The disorder is often diagnosed in childhood.
diagnose after + event
Giving timing information
After introduces the event that preceded the diagnosis.
He was diagnosed after routine screening.
See the difference in context
The same subject can take different constructions because each sentence answers a different question.
Construction
Example
Meaning
diagnose with
She was diagnosed with diabetes.
standard pattern for naming a condition
diagnose by
The infection was diagnosed by laboratory testing.
shows the method used
diagnose in
The condition is difficult to diagnose in infants.
in introduces context or group, not a fixed verb pattern
diagnose at
She was diagnosed at the city hospital.
at gives location
diagnose after
He was diagnosed after a medical exam.
after gives timing
Common mistakes
Some combinations appear in real text but do not mean what learners often assume.
Omitting with after diagnose
Use with before the illness in this structure.
✕ She was diagnosed cancer. ✓ She was diagnosed with cancer.Using by for the illness itself
By introduces a method, not the disease.
✕ He was diagnosed by flu. ✓ He was diagnosed with flu.Quick practice
Choose the expression that matches the intended meaning.
1. The patient was diagnosed ___ tuberculosis.
2. The tumour was diagnosed ___ a CT scan.
3. The disorder is rarely diagnosed ___ adults.
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Frequently asked questions
Can diagnose be used without with?
Yes, if the illness is the direct object, as in Doctors diagnosed cancer early.
Is diagnosed by correct?
Yes. It refers to the test or method used for diagnosis.
Why is diagnose at different?
At usually introduces a place, such as a hospital or clinic, rather than forming a fixed verb pattern.
Related preposition guides
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