# Kitten Not Growing or Thriving: Causes and What to Do A kitten not thriving is one that is not gaining weight, not growing at a normal pace, or not acting like a healthy, playful kitten. In most cases there is an underlying reason, and many of those reasons can be treated once they are identified. The sooner you track the problem and get veterinary help, the better your kitten's chances are. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Weigh your kitten on a kitchen scale every day or two and write the number down. A kitten that is not gaining weight, or is losing weight, needs a vet visit. - A kitten should weigh roughly 1 pound at 5 to 6 weeks of age and about 2 pounds by 8 weeks [1]. - Newborn kittens cannot control their body temperature and need a heat source they can move away from [2]. - Low blood sugar is a real risk in the first days of life because newborn kittens have an underdeveloped metabolism and limited ability to make glucose [3]. - If your kitten is limp, cold, not eating, or not moving, treat it as an emergency and call a veterinarian right away. ## What "Not Thriving" Means in Plain Words Thriving means growing, gaining weight, staying warm, eating well, and acting alert. A kitten that is not thriving is failing at one or more of those basics. Sometimes the kitten is small but otherwise healthy. Other times the kitten is quiet, thin, cold, or weak, and that is a medical problem. Kittens grow fast, so small problems show up quickly. A healthy kitten adds weight almost every day. When the scale stops moving, something is usually wrong. ## Signs Owners Notice The first sign is often the scale. You may notice your kitten is smaller than its littermates or that it has not grown in a week or two. Owners also report a kitten that sleeps more than usual, cries a lot, or feels cool to the touch. Other signs include: - Not eating or nursing well - A dull coat or a potbelly - Weakness, wobbling, or a kitten that is not moving much - Diarrhea or vomiting - Trouble staying warm - A kitten that seems to stop developing while siblings keep growing Some kittens look small but are bright, active, and eating normally. That pattern still deserves a checkup, because a kitten that is not growing can be healthy or can have a hidden problem. ## Why Is My Kitten Not Growing? Causes and Risk Factors There are many reasons a kitten falls behind. Some are simple, like not getting enough calories. Others are medical conditions that need treatment. ### Nutrition and feeding problems Orphaned kittens are at high risk because they depend on you for every meal. A kitten that is not eating enough, or is fed the wrong formula or schedule, will not grow. Orphaned kittens need a warm space, a heat source under part of the nest so they can move away if they get too hot, and a feeding plan matched to their age [2]. Weaning is another common trouble spot. By 5 to 6 weeks, kittens should be fully or almost fully weaned and eating gruel four times a day [1]. If weaning stalls, growth can stall with it. A kitten that is not eating well may also be showing other problems, so it helps to know the warning signs in [Cat Not Eating? When to Worry and What to Do](/knowledge/veterinary-medicine/online-vet-and-care-costs/cat-not-eating-when-to-worry). ### Low blood sugar in newborns Newborn kittens have an underdeveloped metabolism, burn through liver sugar reserves quickly, and cannot make glucose well [3]. Blood sugar can swing in the first hours and days of life. In one group of newborn kittens, average glucose was about 61.7 mg/dL on day one and dropped to about 53.9 mg/dL on day two before recovering on day three [3]. Low blood sugar can be life threatening, and a low number does not always come with obvious signs [3]. ### Hormone and congenital conditions Some kittens are born with problems that limit growth. Congenital hypothyroidism is rare in cats but has been reported in a cat with stunted growth, dwarfism, an abnormal skull shape, and open growth plates [4]. Growth hormone deficiency is also extremely rare, and one reported kitten with stunted growth and low insulin growth factor-1 levels was treated successfully with recombinant human growth hormone over 20 weeks and reached the weight of its littermates [5]. Congenital malformations are another possibility. They are traditionally considered uncommon, but recent evidence suggests they may be an underrecognized cause of death in newborns, and exposure to certain substances during pregnancy has been proposed as a contributing factor [6]. ### Parasites, infection, and other illness Intestinal parasites, viral illness, and other infections can drain a kitten's energy and appetite. Kittens also depend on maternal immunity passed through antibodies at birth and through nursing, and that protection fades over time [7]. Vaccination cannot work well until maternal immunity wears off, so kittens are typically vaccinated starting at 2 to 3 months old, and they should be kept away from unvaccinated cats until the full series is complete [7]. A kitten that gets sick before or during that window can fall behind fast. ### Malnutrition and poor body condition Long-term poor nutrition has wide effects. In one rescued cat, malnutrition contributed to thin body condition, lethargy, poor wound healing, and skin fragility, and the cat's condition improved with nutritional support [8]. Kittens have even less reserve than adults, so poor intake hits them harder. | Cause | What you may see | First step | |---|---|---| | Not enough calories or a feeding problem | Small size, slow weight gain, crying | Track weight daily and review the feeding plan with your vet | | Low blood sugar in a newborn | Weakness, limpness, not nursing | Emergency veterinary care | | Congenital hypothyroidism | Stunted growth, dwarfism, unusual skull shape [4] | Veterinary testing | | Growth hormone deficiency | Stunted growth with no other signs [5] | Veterinary testing | | Congenital malformations | Weakness, poor feeding, failure to grow [6] | Veterinary exam and imaging | | Parasites or infection | Diarrhea, vomiting, dull coat, low energy | Fecal test and exam | ## How Vets Diagnose a Kitten That Is Not Thriving Your veterinarian starts with the basics: weight, body condition, temperature, hydration, and a full physical exam. They will ask about feeding, nursing, stool, and energy level. Bring your weight log with you. A record of daily weights is one of the most useful things you can hand over. Testing depends on what the exam shows. Blood work can check blood sugar, organ values, and thyroid hormone levels. In the reported hypothyroidism case, low total thyroxine levels before and after a thyroid-stimulating hormone challenge helped confirm the diagnosis [4]. When growth hormone deficiency is suspected, insulin growth factor-1 levels can be measured, and other causes of poor growth are ruled out first [5]. A fecal test checks for parasites, and imaging may be used if malformations are suspected [6]. ## Treatment Options Treatment targets the cause. If the problem is feeding, your vet will adjust the formula, amount, or schedule. If parasites are found, they will be treated. If an infection is present, it is treated directly. For specific conditions, treatment can look different. Levothyroxine supplementation was used in a cat with congenital hypothyroidism, and after one week of therapy the cat showed decreased creatinine levels and increased activity [4]. In the growth hormone case, recombinant human growth hormone was given under the skin for 20 weeks, the kitten reached the weight of its littermates, and no adverse effects were seen [5]. Any medication dose for your kitten is calculated by your veterinarian based on your kitten's weight and health. Do not use human medicines or guess at amounts. ## Recovery, Outlook, and Long-Term Management Outlook depends on the cause and how early you act. Nutritional and feeding problems often improve quickly once intake is corrected. Hormone conditions can improve with treatment, as the reported cases show [5][4]. Congenital malformations may carry a more guarded outlook depending on which organs are involved [6]. Long-term care usually means regular weigh-ins, routine veterinary visits, and a vaccination schedule that starts at 2 to 3 months old and continues until the series is complete [7]. Keep your kitten away from unvaccinated cats during that time [7]. If your kitten is also losing weight as it grows, that pattern has its own causes and warning signs, covered in [Why Is My Cat Losing Weight?](/knowledge/veterinary-medicine/symptom-guides/why-is-my-cat-losing-weight). ## Prevention You cannot prevent every congenital condition, but you can prevent many growth setbacks. - Weigh your kitten regularly from the day you bring it home. - Feed an age-appropriate diet on a consistent schedule. Weaned kittens around 5 to 6 weeks eat gruel four times a day, and by 8 weeks dry food can be left down with wet food offered three to four times a day [1]. - Keep newborns warm with a heat source placed under part of the nest, never in direct contact with skin [2]. - Use non-clumping litter for kittens still learning the box, since they may swallow litter [2]. - Follow the vaccine schedule and limit contact with unvaccinated cats until the series is done [7]. - Ask your vet about deworming and fecal testing. - Watch for appetite changes early. A kitten that stops eating can decline fast, and [Why Is My Cat Not Eating? A Vet-Reviewed Guide for Pet Owners](/knowledge/veterinary-medicine/symptom-guides/why-is-my-cat-not-eating) explains what to watch for. ## Limitations and When to Contact a Veterinarian No article can tell you what is wrong with your individual kitten. A veterinarian who examines your kitten and reviews your weight log can. Call your veterinarian the same day if your kitten: - Has not gained weight in several days or is losing weight - Is eating much less than usual - Has diarrhea or vomiting that lasts more than a day - Feels cool, seems weak, or is much quieter than normal Go to an emergency clinic right away if your kitten: - Is limp, unresponsive, or having trouble breathing - Cannot hold its head up or will not nurse or eat at all - Feels cold and will not warm up - Collapses or has a seizure Low blood sugar in newborns can be fatal, and a low glucose level does not always cause obvious signs [3]. When in doubt, call. It is always better to have a kitten checked than to wait. ## Frequently Asked Questions ### Can a kitten be small but still healthy? Yes. Some kittens are simply smaller than their littermates and grow at their own pace. The key is the trend, not one number. If your kitten is gaining weight steadily, eating well, and acting alert, it is likely fine, but a vet check is still a good idea to rule out hidden problems. ### How fast should a kitten gain weight? Kittens gain quickly in the first months of life. As a rough guide, a kitten should weigh about 1 pound at 5 to 6 weeks and about 2 pounds by 8 weeks [1]. Your veterinarian can tell you what range is right for your kitten's age and starting size. ### My kitten is not moving much. Is that an emergency? It can be. A newborn or young kitten that is limp, cold, or barely responsive may have low blood sugar or another serious problem. Low blood sugar can be life threatening in newborns [3]. Call an emergency veterinary clinic right away instead of waiting to see if it improves. ### Can parasites stop a kitten from growing? Yes. Intestinal parasites and other infections pull nutrients and energy away from growth. A fecal test lets your veterinarian find and treat them. If your kitten has diarrhea, a dull coat, or a potbelly along with slow growth, ask for testing at your next visit. ### Will my kitten catch up to its littermates? Many kittens do catch up once the cause is treated. In a reported growth hormone deficiency case, the kitten reached the weight of its littermates after treatment [5]. In a reported hypothyroidism case, activity improved within a week of starting therapy [4]. Early treatment gives your kitten the best chance. ## Related Articles - [Cat Not Eating? When to Worry and What to Do](/knowledge/veterinary-medicine/online-vet-and-care-costs/cat-not-eating-when-to-worry) - [Cat Overgrooming: Why It Happens and What to Do](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/cat-overgrooming) - [Why Is My Cat Not Eating? A Vet-Reviewed Guide for Pet Owners](/knowledge/veterinary-medicine/symptom-guides/why-is-my-cat-not-eating) - [Cat Not Pooping but Eating Normally: Causes and When to Help](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-not-pooping-eating-normally) - [Why Is My Cat Losing Weight?](/knowledge/veterinary-medicine/symptom-guides/why-is-my-cat-losing-weight) - [Cat Weight Gain Causes](/knowledge/veterinary-medicine/nutrition/cat-weight-gain-causes) ## References 1. [Kitten Care](https://www.petpoisonhelpline.com/uncategorized/orphaned-kittens-part-2/). Pet Poison Helpline. 2. [Orphaned Kittens](https://www.petpoisonhelpline.com/uncategorized/orphaned-kittens/). Pet Poison Helpline. 3. [Reassessing neonatal hypoglycemia in kittens: clinical relevance beyond the laboratory value](https://pubmed.ncbi.nlm.nih.gov/42790675/). Topics in companion animal medicine, 2026. 4. [A Case of Congenital Hypothyroidism in Cats: Diagnostic Challenges and Therapeutic Outcomes](https://pubmed.ncbi.nlm.nih.gov/42059300/). Veterinary medicine and science, 2026. 5. [Successful treatment with recombinant human GH in a kitten with suspected congenital hyposomatotropism](https://pubmed.ncbi.nlm.nih.gov/41246431/). Open veterinary journal, 2025. 6. [Multiple congenital malformations in a litter of feline fetuses associated with gestational exposure to a synthetic estrus-suppressing progestin](https://pubmed.ncbi.nlm.nih.gov/42050592/). BMC veterinary research, 2026. 7. [Kitten Care - Cat Owners](https://www.merckvetmanual.com/cat-owners/caring-for-cats/kitten-care). Merck Veterinary Manual. 8. [Suspected malnutrition-induced reversible feline skin fragility syndrome in a cat with congenital axial deformities](https://pubmed.ncbi.nlm.nih.gov/38434166/). The Canadian veterinary journal = La revue veterinaire canadienne, 2024. ## Further Reading - [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners) - [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)