Vomiting after L-lysine in cats

24 reports to the FDA describe vomiting in cats given L-lysine. That is 29% of all reports for this medicine, compared with 18% across reports for all cat medicines, so it is reported unusually often with this medicine.

24Reports
33%Marked serious
54%Recovered
8.3%Died or euthanised
88 daysTypical onset
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How soon it started

Same day
7 41%
1–2 days
1 5.9%
3–7 days
0 0.0%
1–4 weeks
0 0.0%
Over a month
9 53%

How the animals did

Recovered
12 50%
Recovered with lasting effects
1 4.2%
Still unwell when reported
7 29%
Died
1 4.2%
Euthanised
1 4.2%
Not known
2 8.3%

Problems reported at the same time

Loss of appetite
8 33%
Lethargy
6 25%
Liver problems
5 21%
Nasal discharge
4 17%
Blood problems
4 17%
Weight loss
4 17%
Dehydration
3 13%
Ocular discharge
3 13%

Age of the animals

Under 1 year
1
1–3 years
8
4–7 years
4
8–11 years
3
12+ years
8

About this medicine

Type: medicine.

Questions owners ask

Can L-lysine cause vomiting in cats?
24 reports link the two, but a report alone does not prove the medicine was the cause: other illnesses, other medicines or coincidence can be involved. Your vet can judge it for your animal.
How soon after a dose was it reported?
In half of the reports with dates, it started within 88 days of the first dose.
What should I do?
Don't give another dose until you've spoken to your vet, and keep the packaging so you can tell them the product and dose. Your vet can also report it to the FDA (or you can, through the manufacturer or FDA form 1932a).

Vomiting with similar medicines

All reported side effects of L-lysine in cats · Medicines most reported with vomiting