What growth rate is too slow for a child?

Between about age four and the start of puberty, most children grow at least 5 cm a year. Sustained growth of under roughly 4 cm a year in that window is the single most useful trigger for an assessment, even when the child's height is still within the normal range.

When should I take my child to a doctor about their height?

Book an appointment if your child is crossing downward across percentile lines, growing under about 4 cm a year before puberty, is much shorter than the mid-parental estimate with no family history of late development, shows no pubertal signs by 13 in a girl or 14 in a boy, or has growth failure alongside symptoms such as fatigue, poor appetite or digestive problems.

What will the doctor actually do?

Typically they will plot all available past measurements to establish growth velocity, measure both parents, check pubertal stage, and often order a hand and wrist X-ray for bone age. Blood tests commonly screen for thyroid problems, coeliac disease, anaemia and kidney function, with growth hormone testing and, for girls, chromosome testing reserved for cases where initial results point that way.

Late Bloomer or Growth Problem? How Parents Can Tell the Difference

Q: How do I know if my child is just a late bloomer?

The reassuring pattern is a child who is short but has tracked steadily along the same percentile line for years, grows at a normal rate for their age, and has a parent who was also a late developer. The concerning pattern is a child crossing downward through percentile lines, or growing more slowly than expected for their age, regardless of how tall they currently are.

Q: What is constitutional delay of growth and puberty?

It is a normal variation in which a child's biological clock runs late. They are short through childhood, start puberty later than peers, and then keep growing after classmates have stopped, typically reaching a normal adult height. Bone age is behind chronological age. It is far more common in boys and frequently runs in families.

Most short children are healthy. That is worth saying first, because the question that brings parents here is usually driven by a specific worry — a son who has not started puberty while his friends have, a daughter who has slipped down the class height order. The useful distinction is not how short a child is. It is what shape their growth curve has, and that is something you can assess before you ever book an appointment.

The one question that separates most cases

Is your child short but keeping pace — or are they falling behind? A child who has sat on the 5th percentile since age three and grows a normal number of centimetres each year is following a track. A child who was on the 50th at five and is on the 10th at nine has been losing ground, and that is a different situation entirely, even though the second child may still be taller.

Height is a position. Growth velocity is a rate. Clinicians weigh the rate far more heavily, because a healthy body will defend its own trajectory. Falling off a curve means something has been interfering.

Normal growth rates by age

Age	Expected gain per year
0 – 1	23 – 28 cm
1 – 2	10 – 13 cm
2 – 4	6 – 8 cm
4 – puberty	5 – 6 cm
Puberty (peak)	6 – 10 cm

The row that does the most diagnostic work is 4 to puberty. Growth in those years should be steady and unremarkable. Sustained growth under about 4 cm a year in that window is the most useful single trigger for an assessment, even if the child's height still looks normal on the chart — because at that rate they will be dropping across lines whether or not it is yet obvious.

The two common, harmless patterns

Constitutional delay of growth and puberty

The child's biological clock simply runs late. They are short through childhood, enter puberty a year or two behind their peers, and then continue growing after classmates have finished — often arriving at a completely ordinary adult height by 19 or 20.

It is much more common in boys, and it frequently runs in families. The strongest clue is a parent, usually the father, who describes being the smallest in his year and still growing after leaving school. On a bone age X-ray these children show skeletal age behind chronological age, which is reassuring: it means the growth plates have more time open than the birthday suggests.

The hard part is rarely medical. A 14-year-old boy who looks 11 among peers who look 17 is dealing with a genuine social problem for two or three years, and the fact that it resolves on its own does not make it weightless at the time.

Familial short stature

The child is short because their parents are short. Growth rate is normal, puberty arrives on schedule, bone age matches chronological age, and the child tracks a low percentile consistently. Their adult height lands close to the mid-parental estimate — short by population standards, exactly on target for their family.

This pattern needs no treatment. It is the reason clinicians measure both parents at the first appointment: a child on the 3rd percentile with parents on the 3rd percentile is a very different case from the same child with parents on the 60th.

The patterns that warrant a doctor

Book an appointment if you see any of the following. None of them proves a problem exists; each is a reasonable reason to have it checked.

Crossing downward across percentile lines after about age three, outside the expected shuffle around puberty.
Growth under about 4 cm a year between age four and the start of puberty.
Much shorter than the mid-parental estimate — well below the target range — with no family history of late development.
No pubertal signs by 13 in a girl or 14 in a boy. For boys the earliest sign is testicular enlargement, which precedes the height spurt.
Very early puberty — before 8 in girls or 9 in boys. This can shorten adult height by consuming growing time early, and is often the more urgent referral.
Growth failure alongside other symptoms: persistent fatigue, poor appetite, chronic diarrhoea or bloating, unexplained weight loss, frequent headaches, or delayed dentition.
A disproportionate build — limbs notably short relative to the trunk, or the reverse.

What a doctor is actually looking for

The conditions being screened for are mostly treatable, and mostly treat better the earlier they are found — which is the real argument against waiting.

Hypothyroidism. Slows growth markedly and is straightforward to detect and treat.
Coeliac disease. Can present as poor growth with only mild digestive symptoms, sometimes none at all.
Growth hormone deficiency. Uncommon, but a leading reason for referral to paediatric endocrinology.
Turner syndrome. In girls, a chromosomal condition where short stature is often the first and only early sign; usually confirmed with a blood karyotype.
Chronic illness. Poorly controlled asthma, inflammatory bowel disease, kidney disease and untreated anaemia all divert resources from growth.

What the appointment looks like

Bring every past height measurement you can find — the red book, school screenings, old clinic notes. A single measurement today tells a clinician far less than four points across three years.

Expect them to plot those points to establish velocity, measure both parents to calculate the target range, assess pubertal stage, and in many cases order a hand and wrist X-ray for bone age. Blood tests commonly cover thyroid function, coeliac antibodies, full blood count and kidney function. Growth hormone testing is more involved and comes later, only if the first round points that way.

If you want a sense of where your child's numbers currently sit before that conversation, the free calculator on this page compares the mid-parental estimate against their own trajectory and shows a range — useful as a starting point for questions, not as a substitute for the appointment.

Frequently asked questions

How do I know if my child is just a late bloomer?

The reassuring pattern is short but steady — tracking the same percentile for years, growing at a normal rate, often with a parent who was also a late developer. The concerning pattern is crossing downward through percentile lines or growing slowly for their age, regardless of current height.

What is constitutional delay of growth and puberty?

A normal variation where the biological clock runs late. The child is short through childhood, starts puberty late, then keeps growing after peers stop, usually reaching a normal adult height. Bone age sits behind chronological age. Much more common in boys, and often familial.

What growth rate is too slow?

Between age four and puberty most children gain at least 5 cm a year. Sustained growth under about 4 cm a year in that window is the single most useful trigger for assessment, even when height still looks normal.

When should I take my child to a doctor?

If they are crossing downward across percentiles, growing under about 4 cm a year before puberty, far below the mid-parental estimate without a family history of late development, showing no pubertal signs by 13 in a girl or 14 in a boy, or growing poorly alongside symptoms like fatigue or digestive problems.

What will the doctor do?

Plot past measurements for velocity, measure both parents, assess pubertal stage, and often order a bone age X-ray. Blood tests typically screen thyroid, coeliac, blood count and kidney function, with growth hormone and chromosome testing reserved for cases the first round points toward.

When do children stop growing?The timeline, growth plates and how much time is left Growth chart percentiles explainedWhy the trend matters more than the number

This page is general information for parents and carers, not medical advice, diagnosis or treatment. It cannot assess an individual child and is not a substitute for examination. If any of the patterns above describe your child, speak to a paediatrician or family doctor.