Hi everyone,
I’m posting here because I’m genuinely worried and need advice from vets or experienced cat owners.

TLDR: My 4 month cat has fluctuating Diarrhea and lost 20-30 weight over 2-3 weeks.

Basic Info

• Breed: British Blue Point
• Age: ~4 months (confirmed by photo timestamps from previous owner)
• Weight at adoption: ~440–450 grams
• Current weight (today): 420 grams
• Time since adoption: ~3 weeks

Timeline & Symptoms

Day 1 – Adoption

• When we brought him from the previous home to ours, his stool wasn’t ideal but not severe diarrhea.
• Later that same evening, it turned into very severe diarrhea.

First Vet Visit

• Vet diagnosed diarrhea and recommended:
  • Probiotics (twice daily: morning & evening, ~8–10 hours apart)
  • Small-kibble kitten dry food (baby/kitten food provided by the clinic)
  • Supplement paste capsules (opened and squeezed into the mouth)
• Vet told us to continue for 7–10 days and come back for follow-up.

Probiotic Treatment Period

• We followed the plan strictly:
  • Probiotics every single day
  • Kitten dry food
  • Supplement paste
• Important: The diarrhea never completely stopped at any point.
  • It fluctuates within the same day
  • Example:
    • Morning: diarrhea ~5–6/10
    • 3–4 hours later: worsens to ~8–9/10
• Sometimes it improves briefly, then worsens again hours later.

Suspected Eyelash Ingestion

• At one point we suspected he swallowed a false eyelash, so we went back to the vet.
• Vet attempted salt-induced vomiting:
  • Very small amount, adjusted for a ~440 g kitten
  • At most about 1 teaspoon
• He gagged/retched, but did not vomit.
• After salt treatment:
  • Hourly feeding
  • He became lethargic
  • Fully recovered in 1.5–2 days
• During this time:
  • We gave water via syringe
  • Closely monitored hydration

Ongoing Condition

• Throughout the entire process, we never stopped probiotics.
• Diarrhea has been on and off continuously.
• There has never been a stable period of normal stool.

Today – Veterinary Hospital Visit

• Today we went to a veterinary faculty / university animal hospital.
• They suggested that we can and probably should run diagnostic tests.
• However, there is an important concern:
  • At our very first vet visit, we were told that:
    • A 440 g kitten is extremely small
    • Even placing an IV line can be difficult
    • Bloodwork or invasive diagnostics might be hard for him to tolerate or could be risky due to his size
• This made us hesitant earlier, but now we’re at a point where doing no tests also feels dangerous.

Weight Loss

• At today’s weighing:
  • 420 grams
• Meaning:
  • A 4-month-old kitten
  • Lost 30–40 grams over ~2–3 weeks
  • Instead of gaining weight

This feels extremely alarming.

Why I’m Concerned

• Chronic diarrhea lasting weeks
• Weight loss instead of growth
• Extremely low body weight for age
• Probiotics alone don’t seem to address the root cause
• Rapid stool consistency changes within hours
• Diagnostic tests recommended, but concerns about whether his body can tolerate them

My Questions

• How concerning is weight loss at this age?
• Could this be parasites, malabsorption, food intolerance, infection, congenital issues, or something systemic?
• Is probiotics-only treatment enough in a case like this?
• Given his size, which tests are safest and most important to prioritize?
  • Fecal test?
  • Bloodwork?
  • Ultrasound?
• At what point does the risk of not testing outweigh the risk of testing?

Any advice, insight, or similar experiences would mean a lot.
We’re trying to do everything right, but it feels like something critical is being missed.