I used to use Jarrows methyl B12 and source naturals dibencozide sublinguals both from Amazon. I've switched to the b12 oils from Australia. These work out as £40 per bottle when you order 3 at a time. This delivers a much better effective dose and I switched once I got up to 10mg of methyl sublingual mainly since it's a gradual delivery rather than boom or bust, it's absorption rate is around 80% as oppose to the 5-10% of the sublinguals. I take 2 squirts of the oil per day (delivers more than 10mg by a long way) and a bottle lasts a month.