Weight loss after Vitamin B12 in cats

The FDA has received 72 reports of weight loss in cats after Vitamin B12. That is 19% of all reports for this medicine, compared with 4.6% across reports for all cat medicines, so it is reported unusually often with this medicine.

72Reports
71%Marked serious
6.9%Recovered
29%Died or euthanised
7 daysTypical onset
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How soon it started

Same day
8 13%
1–2 days
15 25%
3–7 days
9 15%
1–4 weeks
13 22%
Over a month
15 25%

How the animals did

Recovered
3 4.2%
Recovered with lasting effects
2 2.8%
Still unwell when reported
35 49%
Died
4 5.6%
Euthanised
17 24%
Not known
11 15%

Problems reported at the same time

Age of the animals

Under 1 year
2
1–3 years
5
4–7 years
9
8–11 years
14
12+ years
42

About this medicine

Type: medicine.

Questions owners ask

Can Vitamin B12 cause weight loss in cats?
72 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 7 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).

Weight loss with similar medicines

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