Red flags are specific, well-established warning signs that should prompt a referral for formal evaluation rather than a "wait and see" approach. Below is a working list, organized by age band and drawn from pediatric developmental screening resources (Skillpoint Therapy, "Developmental Delay: Red Flags by Age"; NCBI/StatPearls, "Developmental Delay").
0-6 months: persistent head lag after 4 months; not pushing up on straight arms by around 8 months; not responding to loud sounds or a caregiver's voice; no babbling by 6 months; not tracking faces or following a moving object with the eyes; general lack of engagement or responsiveness to people.
6-12 months: not sitting unsupported by 7-10 months; not rolling over by 7 months; no crawling (or only crawling using one side of the body) by 12 months; not responding to their own name; very limited babbling or gesture use (e.g. no waving); reduced responsiveness to familiar voices.
12-24 months: not standing alone by around 2 years; difficulty developing a pincer grasp (thumb and finger); no words at all by 2 years; a big gap between what the child understands and what they can say; persistent avoidance of peers; emotional reactions that are severe and out of proportion to the situation.
3-5 years (preschool): cannot manage stairs independently by 4-5 years; cannot jump by age 3; frequent falling or poor balance; inability to engage in pretend/make-believe play; difficulty with basic counting concepts; trouble following multi-step directions; little interest in playing with peers; significant difficulty sharing or taking turns; difficulty recognizing emotions in themselves or others.
Beyond age-specific signs, some red flags are serious at any age and should always trigger referral: loss of a previously acquired skill (regression), suspected hearing or vision loss, abnormal muscle tone (either very floppy or very stiff), and a head size that is disproportionately large or small for the child's age and growth curve (microcephaly or macrocephaly) (NCBI/StatPearls, "Developmental Delay").
It's worth being honest with yourself about the purpose of a red flag: it is not a diagnosis. It is a trigger for a referral to a more thorough evaluation -- a pediatrician, developmental specialist, or a formal multidisciplinary assessment. Your job as a therapist noticing a red flag is not to diagnose on the spot, but to document exactly what you observed and initiate or recommend the next step.
Practical takeaway: Keep a printed or digital red-flag checklist for the age groups you commonly see. When in doubt, refer -- the cost of an unnecessary evaluation is far lower than the cost of a missed one, because early intervention consistently produces better outcomes than delayed intervention.
This guide is general information, not a diagnosis or medical advice. If you're worried about your child, the next step is a conversation with a qualified therapist.
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