Lethargy after Vitamin B12 in cats

93 reports to the FDA describe lethargy in cats given Vitamin B12. That is 24% of all reports for this medicine, compared with 14% across reports for all cat medicines, so it is reported unusually often with this medicine.

93Reports
66%Marked serious
15%Recovered
33%Died or euthanised
3 daysTypical onset
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How soon it started

Same day
23 28%
1–2 days
17 20%
3–7 days
13 16%
1–4 weeks
16 19%
Over a month
14 17%

How the animals did

Recovered
13 14%
Recovered with lasting effects
1 1.1%
Still unwell when reported
34 37%
Died
13 14%
Euthanised
18 19%
Not known
14 15%

Problems reported at the same time

Age of the animals

Under 1 year
4
1–3 years
10
4–7 years
8
8–11 years
16
12+ years
55

About this medicine

Type: medicine.

Questions owners ask

Can Vitamin B12 cause lethargy in cats?
93 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 3 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).

Lethargy with similar medicines

All reported side effects of Vitamin B12 in cats · Medicines most reported with lethargy