For children, the best time to start speech therapy is as soon as you notice a delay, and ideally before age 3. Children who receive early intervention services during this window show significantly greater gains in social, emotional, and cognitive skills than those who start later or not at all. For adults, speech therapy should begin as soon as possible after a triggering event like a stroke or brain injury. There is no scenario where “waiting it out” is the better strategy.
Speech Milestones That Signal a Delay
Most parents wondering about speech therapy are trying to figure out whether their child is genuinely behind or just developing at their own pace. The clearest way to answer that is to compare against well-established milestones.
Between 12 and 17 months, children typically say two to three words to label people or objects, building to a vocabulary of four to six words. By 18 to 23 months, that vocabulary jumps to around 50 words, and kids start combining them into two- or three-word phrases like “more milk.” By age 2, most children use at least 100 words and speak in three- to four-word sentences.
If your child isn’t hitting these markers, that doesn’t automatically mean something is wrong. But it does mean a screening is worthwhile. Children whose expressive vocabulary at 24 months falls in the bottom 10th percentile, roughly 13 words or fewer, are clinically considered “late talkers.” Research from the Journal of Speech, Language, and Hearing Research found the threshold differs slightly by sex: 10 words or fewer for boys and 17 words or fewer for girls at that age.
Why “They’ll Grow Out of It” Is Risky Advice
Many pediatricians still default to a “wait and see” approach when parents raise concerns about speech. And while it’s true that some late talkers do catch up on their own, that reassurance comes with real risk. Late babbling can develop into a genuine speech and language delay, and the window for the most effective intervention narrows over time.
The American Speech-Language-Hearing Association has flagged this pattern as one of the biggest barriers to getting children the help they need. Parents are told their child will “grow out of it,” yet early intervention provides a critical window to change the trajectory of a child’s development. If your gut says something is off, requesting a formal evaluation costs nothing in most states (early intervention programs for children under 3 are federally funded) and gives you real data instead of guesswork.
The Case for Starting Before Age 3
Research on early intervention outcomes shows a clear dose-response relationship: more service, delivered earlier, produces better results. Children who entered early intervention as 1- or 2-year-olds showed greater gains in both social-emotional and cognitive skills by the time they exited the program, compared to children who entered as infants with less targeted goals. Speech therapy was the most common service provided in these programs, largely because it naturally targets social communication and cognition at the same time.
Intensity matters too. Children receiving two to three hours of early intervention services per month showed meaningfully greater cognitive gains than those receiving less than two hours. Bumping up to three to four hours per month produced similar benefits. The takeaway: starting therapy is important, but showing up consistently and getting enough of it is what drives real progress.
When Specific Sounds Are the Issue
Not all speech concerns involve vocabulary size. Some children talk plenty but are hard to understand because they substitute, drop, or distort certain sounds. Before assuming this needs therapy, it helps to know which sounds develop when.
Children typically master the “l” sound around age 4, the “s” sound by 4 and a half, and the “r” sound by 5. The “th” sounds come much later, often not fully mastered until age 8 or even 8 and a half. So a 4-year-old who says “wabbit” instead of “rabbit” is developing normally. A 6-year-old doing the same thing may benefit from articulation therapy.
The general rule: if your child’s speech is mostly unintelligible to unfamiliar listeners by age 3, or if they’re still struggling with age-appropriate sounds a year or more past the expected mastery window, a speech-language evaluation is a good idea.
Stuttering in Young Children
Stuttering is a special case because many preschoolers go through a phase of normal disfluency, repeating words or parts of words as their language skills outpace their motor control. This often resolves on its own. But some children don’t recover naturally, and early signs of persistence can be subtle.
Researchers at Purdue University’s Stuttering Project have found preliminary evidence that early delays in speech motor skills and difficulty repeating nonsense words are predictors that stuttering will persist rather than resolve. Children who stutter and also have a separate speech sound or language delay may need a different, more tailored treatment approach than children whose only concern is fluency. If your child has been stuttering for more than six months, if the stuttering seems to be getting worse, or if your child shows visible tension or frustration when speaking, those are reasons to seek an evaluation rather than wait.
Adults Who Need Speech Therapy
Speech therapy isn’t only for children. Adults most commonly need it after a stroke, traumatic brain injury, or neurological diagnosis. The signs that warrant a referral are straightforward: difficulty understanding spoken or written language, trouble communicating ideas through speech or writing, speech that requires extra effort from listeners to decode, or problems with memory and repetition that affect daily communication.
After a stroke, screening for communication disorders typically happens in the hospital. Clinicians check whether the person can understand instructions, perform simple motor tasks on command, and speak clearly. Difficulty with any of these, whether it stems from language processing problems, weakened speech muscles, or trouble planning mouth movements, triggers a referral to a speech-language pathologist. For adults, the general principle is the same as for children: earlier is better. Brain plasticity is highest in the weeks and months following injury, and starting therapy during that period tends to produce the best outcomes.
What Happens During an Evaluation
A speech-language evaluation is not a pass/fail test. It’s a detailed picture of how a person communicates. For children, it typically involves observing how they play, interact, and respond to language in a low-pressure setting, alongside standardized tools that measure vocabulary, comprehension, and sound production.
For both children and adults, a speech-language pathologist will assess receptive language (understanding what others say), expressive language (communicating ideas), articulation (clarity of speech sounds), and fluency (smoothness of speech). Depending on the concern, they may also evaluate breathing patterns, voice quality, or swallowing. The evaluation begins with a consultation that includes the patient and often family members, a review of prior records, and formal testing. Some cases require additional objective testing, such as visual imaging of the vocal cords or measurements of airflow through the nose.
For children under 3, you can typically request a free evaluation through your state’s early intervention program. For children 3 and older, the local school district is required to evaluate at no cost if you submit a written request. Private evaluations through a speech-language pathologist’s office are also an option, though wait times vary widely by region, sometimes stretching to several months. If you suspect a delay, getting on a waitlist sooner rather than later is one of the most practical steps you can take.