I took an extra 25mg of atenolol tonight. I normally just take 25mg. Will it be all right?

Atenolol is a beta blocker used to treat high blood pressure, and cardiovascular disease. Why did you take an extra dose ? You should never increase your dose of medication without your doctor's advise. I don't know what time you actually posted, or where you are, is what I mean. We are not doctors here. Please call your doctor and advise him of this.

ATENOLOL-Usual Adult Dose for Hypertension

Initial dose: 50 mg orally once a day
Maintenance dose: 50 to 100 mg orally once a day
Maximum dose: 100 mg per day

You are probably OK but be very careful with dosage. This will/may lower your blood pressure to the point you may become dizzy. Check with your doctor .