Can I Take Vitamin B12 with Ambien (Zolpidem)?

What the Ambien label lists as interactions

Zolpidem is a prescription sedative-hypnotic for short-term insomnia, taken once a night immediately before bed with at least 7 to 8 hours remaining before the planned time of awakening [1]. Its drug interactions section is short and focuses on other sedating drugs and drugs that change how quickly zolpidem is cleared.

Alcohol, benzodiazepines, opioids and tricyclic antidepressants add to zolpidem's CNS depression and psychomotor impairment, and opioids add respiratory depression risk [1]. Ketoconazole, a strong CYP3A4 inhibitor, raised zolpidem exposure (AUC) 70% and peak levels 30%; rifampin, a CYP3A4 inducer, cut AUC 73%, peak levels 58% and half-life 36%, and the label says that combination is not recommended [1]. Sertraline raised zolpidem peak levels 43% and fluoxetine lengthened its half-life 17% [1]. Vitamin B12 does not appear in that section [1].

What vitamin B12 actually interacts with

Metformin, proton pump inhibitors and H2 blockers can lower B12 levels by reducing absorption [3]. Nitrous oxide can also interfere with B12's function [4][5]. In the Diabetes Prevention Program Outcomes Study, B12 at or below 203 pg/mL was found in 4.3% of people taking metformin versus 2.3% on placebo at 5 years (p=0.02) and 7.4% versus 5.4% at 13 years, a difference that was not statistically significant; each year of metformin use raised the odds of deficiency (OR 1.13 per year, 95% CI 1.06-1.20) [8].

A Kaiser Permanente case-control study compared 25,956 adults with a new B12 deficiency diagnosis against 184,199 people without one. Two or more years of proton pump inhibitor supply was associated with deficiency (OR 1.65, 95% CI 1.58-1.73), and two or more years of H2 blocker supply with OR 1.25 (95% CI 1.17-1.34) [9]. Less stomach acid means less B12 is released from food protein; the synthetic B12 in supplements and fortified food does not need that acid [2]. Zolpidem does not appear among the drugs linked to low B12 in these studies.

Does B12 affect sleep?

The clearest sleep signal comes from methylcobalamin. In a 1996 preliminary study, 20 healthy adults (6 women, 14 men) were observed for 9 days and then took 3 mg of cyanocobalamin or methylcobalamin daily for 14 days. Sleep time fell significantly in the methylcobalamin group, and activity between 11 pm and 7 am rose significantly with both forms. The authors concluded that vitamin B12 influences melatonin and that only methylcobalamin had an alerting effect, shifting the sleep-wake cycle toward less sleep [7]. The dose of 3,000 mcg is far above the 2.4 mcg adult RDA [6][7].

Older reports are case descriptions rather than trials. A 1990 paper described two patients with sleep-wake rhythm disorders: a 15-year-old blind girl whose free-running cycle entrained on 1.5 mg three times daily, and a 55-year-old man with delayed sleep phase syndrome who improved on 1.5 mg daily [10]. Neither had ordinary insomnia.

If you take metformin as well as Ambien

Metformin is where the B12 question usually leads. A 2025 American Family Physician review says universal screening is not recommended, but testing should be considered in someone with at least one risk factor plus a matching clinical feature; features include fatigue, brain fog, depression, peripheral neuropathy and ataxia [11]. A 2017 American Family Physician review lists the situations in which screening may be warranted: metformin for more than 4 months, a proton pump inhibitor or H2 blocker for more than 12 months, gastric or small-bowel surgery, inflammatory bowel disease, a vegan or strict vegetarian diet, and age over 75 [12].

A serum B12 below 180 pg/mL is diagnostic for deficiency [11]. Low B12 can cause fatigue, neuropathy and unsteadiness [11]. Ambien can cause next-day impairment of alertness and coordination [1]. A borderline B12 result of 180 to 350 pg/mL needs a methylmalonic acid test, which confirms deficiency when elevated [11].

Older adults

The 2023 AGS Beers Criteria recommend avoiding zolpidem in older adults, a strong recommendation based on moderate-quality evidence, citing delirium, falls, fractures and crashes with minimal sleep benefit [13]. On the B12 side, the NIH Office of Dietary Supplements advises adults over 50 to get most of their B12 from fortified foods or supplements, because many older adults make too little stomach acid to release the B12 bound to protein in food, while the added form is not protein-bound [6].

Practical points

The adult RDA for B12 is 2.4 mcg a day, and supplements commonly contain 500 to 1,000 mcg; the body absorbs only a small percentage of a large oral dose, and no upper limit has been set because no harm from high intake has been established [6][2]. For correcting an actual deficiency, oral B12 at 1 to 2 mg daily works as well as injections in most patients, with injections considered for severe deficiency or severe neurologic symptoms [12]. The Ambien label's recommended initial dose is 5 mg for women and 5 or 10 mg for men, once per night, with no second dose the same night [1].

Vitamin B12 is available as an oral supplement and as a prescription injection (vitamin B12) [14].